Re: Need help with some direction.
I've got a Schwinn Point Beach (or vice versa) and it's seat tube isn't tapered, I think that's an artifact of the camera angle that makes it look like that. That's one difficulty with aluminum frames they seem to have thicker tubes than steel frames. If you can't get that clamp to fit better than that by grinding it might be worth loosening up the bolts a bit, put some tape on the bottom of the gap and fill the space with JB weld. That might help spread the load a bit instead of just bearing on two points on the tube. The engine's vibration will eventually eat out either the tube or the engine mount if you can't spread the load more evenly around the tube.
Goldwing 1500, Silverwing 600, Schwinn 49