Saw this on the weekend at the semi-annual Slimey Crud Run in Pine Bluff, WI -
I parked the Derbi and my buddy's Bultaco next to it -
Bimota V-due, 500cc 2-stroke (https://en.wikipedia.org/wiki/Bimota_V_Due
This one has been totally redone to actually work. Long story, that I got from the owner, but basically the engine cases were a problem originally. By the time Bimota figured it out they were almost broke.
Factory engineer bought everything (bikes that were bought back, unassembled bikes, all parts) and had new cases made, as well as going to carbs instead of the problematic F.I.
First one I've ever seen.