Re: how/where to beef the frame up
Studying that frame but not knowing your weight and the riding surfaces you usually travel, I've added a couple of gussets where I would add them if I were building that bike. The red ones for sure and the purple one unless you can incorporate some strengthening in your motor mount. I'd probably use 1/4" plate but 3/16" would suffice, I'm sure. That is an interesting looking chassis and should make a great looking cruiser. Keep us informed.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"