The airbleed passage is opened by the movement of the throttle barrel, and has a very strong "on/off" characteristics. For methanol/glow ignition this is less problematic since the mixture strength affects ignition timing, and the "system as a whole" has some self-correcting tendencies. Gasoline and spark does not show that tendency.
This makes finding a good tune next to impossible, even though on the bench the engine appears to run OK. In the air, conditions change, and any issue with carburation will present itself rather clearly.
A twin needle carb has a much smoother transition between full throttle mixture and the lower throttle regions, and that is allready near impossible to find a decent tune (with the exception of the SuperTigre carburettors, or maybe the Lötterle, but those are very exotic and nowadays extremely hard to find).
The airbleed principle does not lend itself to modification (grinding the slanted groove), since there IS no slanted groove to grind
Leaves only the solenoid solution.
Twin needle carbs can be modified, but that is a bit of a hit&miss affair. Once you have done a few, it is not too difficult, but especially the first one is a matter of sheer luck.

I made the same mistake initially, thinking the engine ran well on the ground, and taking it to the air, well... it flew, but was not much fun: Throttle response during landings and go-arounds is more important than one is led to believe when being used to crisp responses...

And the mess a poor mixture makes also stops being fun rather quickly...