I Like the Rob English bottom bracket idea. I am thinking we could adopt that. Just don't have an idea yet how the bottom bracket shell swivels.
SW, it would be great if you can add some dimensions to that sketch. Then we can pin geometry down. I was thinking because the Ti Swift works so well, we could use its geometry to design up a M60-like frame.
funny that you should mention the Rob English bb. although i forgot to indicate it, that's exactly what i was thinking of when i made the above drawing. I would be happy to make a proper drawing of this concept with correct dimensions. Can you send me the drawing with dims you made for producing the Ti Swift?