This is what I was considering as a mixer, right after the air filter, at the beginning (top) of the elbow from the previous post.
1pcs LPG CNG Gas Mixer for Bi Fuel Conversion on Motorcycle | eBay
The only thing I am wondering is will there be enough air velocity to trigger some vacuum and feed propane right after the air filter?
I struggle to find a place my feed tubes/venturis lower in the elbow, near the carb. There is just no clearance to create a thicker gasket/feed plate between the air intake and the carb.