Bert,
My very rudimentary test and intuition seemed to hit the sizing for the valve quite close on this first try. The "max opening" is in a good range. I'm assuming as the engine size increases and the intake volume follows an upsize in the valve might be required. My initial test were with a fuel needle valve and that didn't work as it didn't flow enough. The testing showed response when I simply squeezed a larger fuel tube attached to the intake so valve size was determined off that. One thing to mention is this engine would not run mid range without the valve - its just way to rich.

Flight dynamics might have an effect as you noted and that remains to be tested. I am using the muffler pressure/Crap trap as we know that is proven. The Intake "pull" should follow RPM so I'm thinking that might be somewhat self correcting at least in mid range and higher. Next plans are to try this on a "baby" (.40) four stroke and a two stroke to see it its repeatable across different engines. Want to make sure this test on the .91 is not an anomaly.

One thing that impresses me is the throttle response with this setup - No slowing of thottle servo is required. Im assuming the Bleed flow might be "self correcting" as the throttle is opened quickly ( Intake suction drop) and enriches the mixture to get the engine sped up - Like a mock accelerator pump.