I'm guessing you're going for twin carbs as it's too difficult to get a single carb in there?
Anyway, the older Triumphs ran a 2 into 1 cable setup...a single cable from the throttle which then went into a plastic cylinder where 2 cables came out.
I think maybe some 2 strokes used them as well...1 cable for the carby and the other for the oil pump.
I've got an old vacuum guage that I used to sit on the tank of the Guzzi 1000s with a 3 way gas tap connecting hoses to the carbies.
I'd take the bike for a run and at different speeds, would turn the tap to get a reading on either cylinder and then stop and adjust. Seemed to me to be more accurate than a stationary adjustment where there is no load. You're welcome to use it when the time comes.
Anyway, good luck. Can't wait to see how it turns out