@Nick That's pretty cool. Besides the carbs being different do you know how it's managing opening the second carb at 1/4 throttle?
I know one possibility is definitely by messing with cable slack and cable adjusters on the throttles and carbs to adjust the timing. The larger challenge tho would be to change the RATE at which one of the throttles opens. Does that second throttle cable actually pull at a faster rate?
Like someone mentioned above I guess you'd be looking at some kind of exponential pulley system. (edited)