The DIY Home Built Motorized Bicycle (non kit) seems like an appropriate forum really.
I agree, these is such a thing as just too many forums to pick where to post or search.
A good title for searching on should make them easy enough to find.
That said a father and son here in Phoenix opened a commercial MB store early this year, Redemption Bikes. they went under a couple of months ago but at the end there they were into those Push Drive Motors.
I didn't get a chance to ride one but I got a good look at them.
Two thumbs up for a motorized trailer you can just 'hitch up' and move you around like a bat out of **** with no laws for certain trips like long commuting.
Just un-hitch it for parking, storage, or just plain pedaling without extra weight.
In fact I can even see a trailer with some cargo space too for hauling stuff if it has brakes as a push drive.
What I can't see is me riding one as my main bike which is how I get around.
I know how I ride and where I go, the last thing I want to have to do is constantly account for a trailer when I turn or park, that would drive me crazy.
That and I like to feel the balance of the bike and the power direct to the road, I don't think I would feel very 'in control' with my drive force being applied at the seat post, I know first hand from many a bigger trailer hooked to a vehicle how it feels when they bounce out of control or you can't stop quick enough and you jackknife.
(shivers) Ya, bad memories, not from being hurt, no accidents at all, it was the sheer unadulterated fear I had riding them out I want to avoid, especially considering on a 4 wheel vehicle with a low hitch it just slides your ass end around. On a 2-wheeler with the hitch under your butt it's just as likely to throw you and the bike to the ground and then run over you, hahaha, or not ;-}