The engine leans out well on the mixture controll, I will start on a rich setting and then lean it out till just before it leans to much so as for fuel supply I am getting the max I can. The throttle does open all the way.
I will try some more thrust tubes to see what they deliver thrust wize, I am not after speed but power for takeoff so in theory a larger outlet is called for.

Some more measurements wrt 85, 95 and 105mm outlet should give me the data I need.
Just a PITA to have to make a new tube and remove the fan to install it every time....ah well the joys of DF LOL
The hassle is that i live in an estate and noise is not permitted so I have to time my tests carefully not to make hassles with the people arround, I must admit this BVM is extremely loud!

Theuns