Just threw some old junk on the frame and used toilet paper and packaging foam as spacers to make it fit. This thing really is a work of art !
Still not sure if it's the right size though. The seat is set at my usual position (67cm from BB center to top of saddle).
I have enough room left to raise it 5mm without any special tricks, and another 5mm if I use 170mm cranks. It really is borderline.
Top tube C-C is a few mm shorter than my Bulls though. I'm liking that. I'm leaning towards keeping it, but not entirely convinced yet.
Regarding the 20" idea : with a 100mm fork, the BB axle is currently 12.5" from the ground.
That becomes 9.5" if I put 20" wheels on it, or nearly 10" with very thick tyres (Schwalbe Big Apple 20x2.15 for instance).
Add an extra 5mm by means of a 170mm crankset, and the pedals' BDC (*) is still 1.5" lower than on my Sbike, which is already extremely low for being a sporty model.
With some clever measuring and drawing, I'm pretty sure I can come up with a new triangle for the linkage. That could raise the bike an extra inch at the back.
* : Bottom Dead Center, for those who aren't familiar with the acronym.