Where do you get your "generic types", and are they snug?
I used to order motors from BMS Battery in China and that was the time to stock up on the little stuff I like, such as TA's, left-hand, Half-twist throttles, 9-pin connectors, etc. Their Ta's are good and the stuff is dirt cheap. But I doubt you would want to pay the freight from China for TA's.
I just ordered a pair off Ebay and they were a sloppy fit even though they were stated to be for 12mm axles. I used them anyway because I could easily fit two and it's a low-powered system. Whether or not you want to spend the $$ for Grin TA's, depends on the system power and whether or not you can fit two. You haven't told us much about your build except that it's a 500 W rated Bafang. It could be a 12mm axle SWKX (whatever) motor or it could be a 14mm BPM.
Thanks for your advice, and also to the fellow who mentioned filling dropout slots deeper.
That makes me wonder if you can possibly leave the slots alone and grind the brake mounts to restore full pad contact, or at least keep slot filing to a minimum, just enough to get radius correct at the top for full contact.
No, don't touch the brk. mounts
How much futzing is required for a rear hub fitment varies greatly from bike to bike. Although all my donor bikes have been high quality, my hand-built Rocky Mountain was a pain to fit these wide (that's the rub , literaly), geared mini motors. My Taiwan GT's were very easy. Little filing, few spacers and little or no "dishing" to center the rim.
Likewise, the Taiwan made Motobecane (Great bike, did you get yours from Bike Island?) looked easy. I did a frt. mount, but I tried a rear motor to get an idea how it would fit. It dropped right in and the only filing looked to be the usual 'rounding" of the deep end. The key to gd. fitment is using the correct "C" washers(not the ones w/ the tab). In the pic you will see the round boss surrounding the drop-out slot (the inverse is a round recess w/ "lawyer's lips" around the perimeter). Only file the slot to center the C-washer on the round boss/recess.
Depending on how wide the motor/cassette-freewhl is, a flat washer may be required between the end of the cassette and the inside of the drop-out to keep the spline from rubbing(washer w/ tab is ok for this.
I get a kick out of the promotional advertisements that say you can install a kit in under an hour. Maybe if you're a pro who's done it a dozen times and has a shop full of ebike odds and ends...
No, that's joke. I've maybe done a dozen builds and even a much simplier frt. mount takes me hours. But I customize all my cables to length and make all my controller connections. l like things tidy and stealthy