I based my version of the rear small basket 3-1/2" rear-ward relocation on this idea.

I used 3/4" x 1/8" X 13-1/2" aluminum instead of 1" wide material and stainless steel (SS) 5mm fasteners, four SS 5mm lock nuts. I had all of these items other project.

I drilled a 5mm hole in each of the small basket rectangular bottom members. These new holes in the small basket were aligned with the existing rearward threaded holes on the bike rack.
 
The bike rack original forward threaded holes were used to secure the 3/4" aluminum to the rack.

The original 4 holes in small basket bottom members were used attach the basket to the new aluminum pieces. I used 5mm stainless cap head steel bolts and nylon lock nuts.

The two aluminum pieces were painted black before installation.

Thanks for the information on relocation of the rear basket, PERFECT!

Still smiling. Added an Ergon ST Evo Core saddle. Much better cushioning for the greenbelt root bumps and mild washboard dirt roads. The Ergon saddle is narrower than the stock saddle and much more comfortable.

Added two zip ties to each loop on the rear bag. I have the small RadPower rear basket and bag. The bag attachment straps were not sufficient enough to prevent the bag from bouncing upward. I added a piece of ~5mm foam liner to bottom of the bag. My thought is that as the items in the bag move around when underway their wear and jostling will be dampened by the foam and the bag bottom will not be abraided. I carry an iPhone inside a foam envelope in the bag as well so I am attempting to dampening this item as well.

I carry a spare tube, road side tool kit with 3 extra zip ties, a pump, a ~5mm x 2M braided wire cable, 3# Master combo lock. This light weight lock is for when I stop and can keep eyes on the bike or use a restroom along the ride. I would not recommend this lightweight lock for an unattended bike left in a public location.

I ride with a Dinotte light front and rear, yellow in daylight, white at night.

Nothing has come loose or fallen off the bike. Small amount of intermittent rear brake squeal, especially if I only apply the rear brake without the front brake as well. I need to loosen the rear caliper and realign it with the brake applied to solve eliminate the squeal.

I am riding predominately in Mode 2 & Power Level 2. I can easily ride 55+ miles in these settings. I use a 100w Renogy solar panel to charge a Renogy power bank. I then use the power bank to recharge the bike battery and the Dinotte lights. I now have an off-grid e-bike.

I have been inflating the tires to 45 psi. I will now ride the bike at 35 pi's for a while to see if I can dampen the ride a bit.

I am thinking about how to relocate the small metal basket rearward about 2". I want more clearance between my rear end and the front of the metal basket. I do not hit the metal basket but I do feel the nylon basket rubbing.

 If you had fabricated some type of bracket to accomplish this relocation, please post info. 

My initial thought is a 3D printed carbon fiber PETG bracket with two holes that I can bolt to the basket and then bolt to the bike rack. This bracket would allow me to mount the basket more rearward. I am reluctant to drill new holes in the basket as there would not be sufficient edge distance clearances for any additional holes.

200 mile review updates
Installed Tannus liners (foam inserts), schwalbe tubes, and Schwalbe Al Grounder 29x2.5 tires.
I like the ride better with these tires. I should be nearly flat proof with this setup.

Also rigged up a rope and pulley hoist lift in the garage. Using this lift allow me to easily raise the bike off the ground and then attach the Park Tools bike stand to the seat post.
I purchased the hoist lift from Harbor Freight for $16. This tool is designed for hunters to field dress large animals like deer and elk.

I attached a short loop of 1" webbing around the seat post and the used a carabiner to attach to lower pulley.

Like it a lot!
I have ridden over 100 miles. Here are my thoughts.
Glad I bought it and decided on the Regular and not the Large. 5'9, seat height of upper limit of seat-post. (The pedal to seat top distance is ~31.5", which matches my two other bikes, mntn and gravel)
Assembly was straightforward, except the front fender rubbed on the rear lower right sidewall. I spent +1 hour trying to get a good non-interference fit. Solution was to mount the fender at the crown with the bolt centered vertically in the slotted bracket and to bend the left front fender wire brace loop towards the front of the bike. I test fitted the fender several times to determine how much of an angular bend would be required on the left wire brace loop in order to move the fender to the left and away from the right side of the tire sidewall. I bent just the wire loop on the left wire brace towards the front of the bike approximately 15 degrees. This bend pulled the lower end of the front fender to the left and away the tire right side of the fire sidewall.

I added four pieces Orcal 631 transparent to the frame locations where the frame might be scratched. I wrapped the horizontal frame segments with this clear removable plastic where I step thru the frame and where I secure the bike with straps to my 1UpUSA bike rack. I will add more Oracal 631 transparent film where the chain slack hits the top side of the frame between the rear wheel and crank arm.

I added Crank Brothers pedals, STAMP Gen 1. I like this pedal, they are larger and provide a secure grip to sneakers.

I added Eergon Grips GC1. This grips are larger diameter and are a better grip as compared to the stock grips.

I use the small rear bag in a small rear rack. The rack is quite secure and the bag fit snug and is secured with a velcro fastener on each side. I secure the bag when full of groceries with 3 Radpower elastic straps with hooks.

I use Dinotte Lighting  front light and rear light. Dinotte lights are  are BRIGHT ! Been a user of these lights for over 10 years without any issues. They are great quality and the brightest lights available, period.
I use a yellow light during daytime and a white light and yellow light at night.
This illumination is a much needed improvement as compared to the stock headlight and taillight.

I added a Cascade Designs Bottle Cage Mounting Bracket for Rad Power Bikes and two Blackburn Chicane Water Bottle Cage (Stainless Steel, One Size). I added 2 Rad Power water bottles. All fit well and snug. I uses shorter bolts to secure the bottle cages to the mounting brackets. The stock bolts were about 10mm too long and very close to the head tube.

I added a Rad Power mirror and removed the bell. The bell will not be used and it was in a very awkward position. I like the mirror, very stable and if mounted tilted forward quite a bit, the entire field of view excludes the rider completely.

I use the phrase BOOB. Battery, Outlet, Outlet, Battery. This means I first plug the charger into the BATTERY, then I plug the charger into the OUTLET. After a full charge, I unplug the charger from the OUTLET and then I unplug charger from the BATTERY.

Before riding I use the phrase KOOB. This means KICKSTAND, OFF, ONE, BRAKE
This means I use the following actions when mounting the bike, KICKSTAND up, make sure the bike is OFF, make sure the bike is in gear ONE, and my right hand is on the BRAKE. This method ensures that I do not inadvertently grab a handful of throttle whilst mounting the bike. The Radster is the only bike I own that has a kickstand so I am prone to start riding with the kickstand down (Did this during several test rides at the LBS.)

Once I stop riding I turn the bike off before dismounting. This way I do not inadvertently grab the throttle when dismounting.

Bike is stable, rides well, and the range is as advertised. I ride in either mode 1 or 2 and rarely set the PAS above level 3. I have used Mode 3, in gear 8, and verified the bike will attain 28mph. Very FAST.d

Handle bar positions is rotated slight to the rear and tire pressures are 31. Front shock is 2 turn clockwise from center. I always ride what the suspension in unlocked mode. Ride is firm and comfortable, but I do not intend to curb hop on this bike..as it is not a full suspension mountain bike.

I like the steering geometry and rider position. I find the bike very comfortable when properly adjusted to my preferences.
The battery charges nicely and is HEAVY. The battery deserves a two handed grip whilst carrying it.  I 3D printed these two parts for the battery and for the RFID tag.

Rad Power Bikes Safe Shield Battery Cap
https://www.printables.com/model/940491-rad-power-bikes-safe-shield-battery-cap

Rad Power Bikes RFID Card Holder
https://www.printables.com/model/937790-rad-power-bikes-rfid-card-holder

I will be replacing the tires with Schwalble AI Grounder 29x2.35 tires and tubes. I will also install Tannus Armor Tire liners.
The stock tire are marginally tread, shallow and do not feel as secure in aggressive cornering at speed or idle. I prefer Schwalbe tires and considered installing Schwable Marathons, a proven durable tire. I am nervous the stock tire and tube are not sufficient to prevent flat tires, especially goathead punctures. (This quite common here in Boise)

In addition to water I carry the Radpower road side tool kit. IF and when I have the dreaded flat tire I will need to add some method to hold the bike upside down without damaging the controls. I have a couple of ideas for the Prusa MK4 3D printer, stay tuned.

400mm Radpower Seatpost

https://www.printables.com/model/40331-radrunner-front-rack-rad-power-bikes-20-x-20-x-16-/comments

Printed this front rack on a Prusa MK4 with carbon filled PETG

https://www.printables.com/model/40331-radrunner-front-rack-rad-power-bikes-20-x-20-x-16-/comments

Printed this front rack on a Prusa MK4 with carbon filled PETG

7/5 Update
Will not fit on a Radster Road, inteferes with cable routing whilst turning.
I will donate the build to a local bike non-profit.
The Roadster Road front geometry/4 bolt pattern is designed for a rack that is mounted with the platform below the 4 bolts, not above the 4 bolts.

Has anyone used the Radpower Throttle disconnect kit? How much did it cost?

Do you know what make and model motor is used in the Raster Road ?

Park tool makes a great T handle adjustable torque wrench

https://www.parktool.com/en-us/product/adjustable-torque-driver-atd-1-2?category=Torque+Tools

Ordered A Radster Road, Regular size, blue color. Radpower website, they included one accessory ($100 or less) I choose the small basket. Stay tuned.
Going to build with Crank Brothers Stomp Large pedals and Tannus foam liners.
I run the same pedals on my mtn and gravel bikes..I like them.
Thinking about running on Schwalbe Al Grounder tires as well.

I rode the Radster Trail as well, just not a fan of a "fat tire" bike.
I did not like the rolling resistance and turning feel of the Radster trail with the 27.5x3" tires.
I am a big fan of 29x~2.5 or slightly less wide tires.

Thinking about buying a Radster Road Large. Problem is the rear fender on the Radster Road will interfere with the securing arm on a OneUpUSA bike carrier. The securing arm on the bike carrier needs to touch the wheeel at about the 9 o'clock position.

Will the Radster Trail rear fender (it is much shorter than the road model fender) bolt up/fit onto a Radster Road? Are the Trail and Road bikes identical enough to use a rear fender from the other model?