I still strongly stand behind the '77 VM20 intake. While it wasn't perfect I was able to mod mine to use the stock airbox hole and everything.
Still suffered from having to work around frame clearance, but it was a good idea. Main reason I sold all my hobbit stock was because it seems everything performance-wise that get's built for them is a workaround, rather than a solution. The long-dong, out the side intakes are all not ideal for a hi-rpm, peaky setup where you really want that carb as close to the reeds as possible.
I really wish someone would start manufacturing rear-clutch adapter shafts for these transmissions, and remake the minarelli hori adapter shafts for vespa while you're at it.