thought I would add a photo

BTW - I recently completed the gearing change.   I installed a 3 speed freewheel - yes, Chinese replacements are still available out there in ether-land, right off Amazon - and a vintage Suntour VGT Luxe derailleur I had on hand along with the matching friction shifter from what I showed above on the left.   Just what the Dr. called for - rear cogs of 16/19/22 in combination with the front 48/38 lets me ride this much of the time like a bicycle and hit the boost when I have a bad headwind or a hill.  It also got rid of the proprietary chain tensioner used by RAD.  I can now climb most light grade hills in level 1 or 2 without too much effort - all up to the rider and their desire to get a workout vs using the throttle.   If anyone wants pictures and some guidance on how to do this, please contact me offline.  If you have sources for some parts, or have a parts bin from your bicycle hobby, this is an inexpensive and a major upgrade to the bike.  The hardest part was finding a derailleur hanger - I used one from a TREK 7100 that I was able to modify in about 20 minutes with hand tools for the job.

PS - I had to add a spacer on the hub to assure that the derailleur did not touch spokes.   My measurements say I could have installed a 5 speed freewheel (barely! - but without a spacer), but it would have been so close, with minimal added benefit, that I did not go there - even though I have several 5 speed cogs in the parts pins.   The driveline alignment with the spacer and 3 speed freewheel is about perfect - another reason I did not bother with the 5 speed rear hub..

Sorry about the belated reply - I swapped out the entire battery and base plate, and purchased an adapter from XT60 to the odd round connector RAD uses.  I used the RAD battery for a 350w ebike conversion I performed last fall on a 1975 Motobecane Grand Touring, which is probably the only 21 speed, hybrid configured you will ever see.   The 10.5 battery is fine for the smaller battery and weights a bit less

Been using my Radmission on the great rails to trails up here in Wisconsin.  Got it a bit less than a month ago - in 16 days prior to a business trip hammered out well over 300 miles on the trails.   Age and other physical issues are catching up with me, why I went to an ebike.

The Radmission is has adequate power, and if you look a couple posts back, I modified mine to a 2 speed front to give me a low range when I need a little more pedal grunt, to help the motor up something a tad more steep, or when it calls to run slower than a 50:16 gear ratio allows.  My only real complaint with the bike is the battery capacity, which at 10.5ah is easy to burn up in a couple hours.  I recently upped mine to a 13ah which helped a bit.  All other Rad bikes come with a 14ah, but also have larger 750w motors to burn it up with. 

The system does not really estimate "effort" like a torque system does - but that is a separate discussion.

Using 2 sprockets, the larger of which is a 48 (vs the stock 50) and the smaller being 38 gives you two fallbacks.  First, if you live near any kind of hills the 500w hub can be a bit underwhelming, so dropping back to the 38 tooth front gives you more leg power to the wheel in the form of torque.  The 48T sprocket compares very closely to the stock 50, just what I had on hand since the type of stock sprocket used is rather plain and does not behave with the shifter.

Anyway, just sharing an idea that I consider an improvement.

I have also done this and replaced the saddle - the seat is also part of the comfort issue.

I used a simple in line post, similar to this one that I had in my toy pile

https://amzn.to/3Fy2CNK

The kickstand, also out of stock at RAD, this one works perfectly, includes the correct screws.
https://amzn.to/3HI7x0j

Seat is up to you, can give you some suggestions on that also, but that is more of a personal taste. 

BTW - one tech error, these are 110BCD chainrings - still easy to get hold of - I used a set of vintage Shimano Biopace rings, you can grab a complete crankset with chainrings in decent shape on Ebay for around 40-50 bucks if you shop a bit.   I've put about 50 miles on this in 2 test rides and it works well - I shift back and forth as I feel fit base on how fast I want to go and how much pedal I want to use versus motor. 

OK - so I purchased a Radmission knowing that some things could use improvement based on the price point.  Among what I feel are shortcomings is the single speed chain line.    Where simplicity is king, and some folks get into this, the single speed is where to go.   However,  your torque input to the pedals is fairly low given the 3.125:1 stock gearing, so the result is poor battery life.   In hilly SW Wisconsin I was getting around 25-30 miles per charge down to empty.  Once you get below about 50% battery the driveline starts to struggle.

I have successfully converted the front drive using a pair (48/38) of 130BCD chainrings, proper spacers and bolts and a vintage derailleur - all from my unloved toy collection.  The derailleur was a trick, as there are limited positioning options and this one worked with only a repositioning of the controller up the tube.  An old Sun friction shifter on the left bar below the controller interface (I actually used a right one on the left mounted upside down as I like the way that shifts - backward, but easy to use) and routed the cable down the down tube along with everything else.  I added a nicer chain guard, as the stock unit is pretty drab.  The only last thing necessary was to increase the tension on the chain tensioner by 1 spring point (look at install instructions for that item and you will know what I mean) and I now have a 2 speed front end.   FYI, I doubt the stock tensioner can take up more than 10 teeth - and I might change the 38 out for a 40 as it is near it's limits with this configuration.

With the low range gear (2.375:1) I can keep the boost at a 1 or 2 and ride comfortably at 14+mph for the 1st 3 bars of the battery b4 it drops off.   Due to gearing and simply the cadence that is comfortable with the stock gearing, I used to ride at 16-17mph at boost 2-3.   Due to the improved ability to get leg torque to the wheel in low range, battery life has increased to 30-35 miles/full charge, or about 20%.  Also, generally climbing hills or pedaling with no boost (read as dead battery or broken electronics) is easier to manage (obvious).

On high range, a 4% reduction from stock to 3:1, I can tool along all day at 18mph without feeling like my legs are flailing.  (if you look at the math here, about the same cadence at 14mph low range as 18mph high range.

All changes are completely reversible.

Posting this so other Radmission owners can contemplate the benefits.   Total conversion cost, even if I had to find a new derailleur which would do the job, should be around $125-$175 depending on brand of components used.  Of the tweaks I have done thus far, this is the one that has had the most positive impact on rideability.   Keep in mind this is from a 62 year old trail rider who is putting down 18-22 miles a day on this machine every day - at least until the snow flies.

Feel free to contact me with any questions, I will try to help.