I used a 12mm Motobecane intake (stock) to connect the reed block to a 12/12 Dellorto (stock from a Vespa). Then, I cut the sidecover mount off.
The result is a carb that is easy to pull off the bike without removing the engine.
The result is also slooooow. PA50I with a 12/12...
Anyway, you could duplicate this project with bigger parts, and still nest the carburetor deep in the heart of your hobbit. A 14/14 is about the same size.