Great minds think alike Bert... Working on a compact and simple design but was struggling a bit. My mind works funny and most "solutions" come to me at night apparently and manifest as soon as I awake. Trying something now that came to me this morning that might be a valid solution. Attached are previous try's that all had promise but were not easy to package. The ability to print this would also be of great benefit for "distribution"

The valve must be somewhat linear and have good repeatability. While at first I thought an airtight seal was necessary, I have found that a small leakage under vacuum is actually beneficial. If sealed very tight, the tube at the takeoff can accumulate some vapour and fuel droplets and choke the engine when coming off idle.

Nowhere near dethroning the solenoid yet as much testing to be done - The Magnum 91 is impressive though as I have never seen such a smooth running and happy engine on a bench - converted or not. Unfortunately I don't have a plane of that size to bolt it in readily. When I finalize a simple valve I will get it in the air on something.