I took the bike to a shop and they indicated the 16T freewheel is as small as it gets on that hub. The only alternative is a larger chainring on the crank.

Has anyone replaced the rear cog on the radrunner1 with something smaller? I live in a flat town and any power assist above level one basically means the battery is doing all the work. I think it comes with a 16 tooth cog, is there a bolt-on replacement at like 13 or 12 teeth?