Funny. Who’s office is that? On the maximum throw comment. Think about this. If you have a 15mm and a 19mm carb, the single cable on top will only open the 15mm carburetor and the 21 will still have like 5-6mm to go but can’t. A one millimeter difference in carburetor bore between the two you can get away with but that’s about it.
The carburetor bores between your two need to be damn near identical.