Well, I'm mostly hoping to figure this out for my Poison Apple muscle trike build. I don't know if you saw the latest update to it, but I'm thinking of removing the seat tube and original top tube, and converting the frame into a boy's cantilever style frame, sans seat tube, but with the headset angled back and the tank portion all welded to the frame. Like this bike, I plan to put the seat over the rear axle, except mine's a trike, and the rear axle is behind the bike frame. I want to know if my idea would still be strong and rigid enough to work, especially with a 250lb guy riding it.