Thanks so much for the detailed reply. (FYI, I'm a 65-y.o. guy & weigh about 115 soaking wet, so I should be able to break the sound barrier .)

I currently own a 250-watt L-1 purchased from R. Martin about 5 years ago. It's very sturdy, but I can hardly move it when the wind is howling, & the battery quickly drains. Too bad, because I've never had a broken spoke, even on the rutted dirt roads here. BTW I plan to install No Mor Flats inner tubes when I get a new e-bike, same as I have on my L-1, so flats shouldn't be a problem.

Looks like MiPower is the way to go. Thanks again for your help!