Cut seat tube at the top, put straight seat tube in, that gives you the mm angle for vertical 212. With head tube angle it looks like, if you flip the bb around to the front side of the down tube, your set.
Or...fab a mm for vertical 212 with existing seat tube, cut off bb and place it behind mm. Changes your seating profile, but no need for running a long chain with idlers to back wheel. Which would be needed for the above....gonna be neat seeing what'cha do
See the engine mounts from ghettobike.com - two block style aluminum mounts with a hinge for a plate to mount the predator to.
If you wanna go custom, I suggest you pick up some 1/4" steel and cut a motor plate, then weld it to a triangular piece that is mated and welded to seat and bottom tubes.
