Thank you for the info.
Note that the difference between 7.0 mm (.276") and 7.5 (.295") is *massive*, a huge difference - using a .157 spraybar (4.0mm), it goes from 0.0189 square inches of choke area, or 0.0243 square inches. ** 33% more ****. That is nearly the entire range of usable systems for stunt. You are much better off starting smaller and working up, because it will at least make it needle properly. If, when it's otherwise working OK, and you want to adjust the power slightly, you might go up by ** 0.1 mm ** ( .004"). That will take you 0.0189 square inches to 0.0199 square inches.
Venturi size is a very sensitive adjustment, you need to think of it in a single-digit thousandths of an inch, not tens of thousandths, and tenths of a mm, not 1/2 a mm.
Brett