OK guys, thanks for the input.

Dar, that is correct, the rules in this racing class limit the venturi diameter to 4.5 millimeters. And since we are racing, and running the engine above 20.000 rpm (hopefully), a properly shaped venturi is important. So no choke plates...

Another question: does the needle valve of the .49 Akrobat fit the .21 engine? The one of the .15 is slightly too short...

Pé, why aren't you using the MVVS venturi on your .15? Just experimenting a little?