RE: Overloading an engine
Dave,
I won't cringe, since MVVS specify up to a 15x10 on the .91...
Also, I am not surprised at its slight disadvantage on the same prop, compared to the Webra 5 port engine.
The webra, which has a 17 mm crankshaft, has a larger gas passage and it runs better with a muffler, while the MVVS is more inclined to use a tuned-pipe... And with a large prop it will need a long one.
With a long tuned-pipe, Mike Billinton got pretty good results with the Super Tigre, in [link=http://www.supertigre.com/engines/supg0235-man.html]this MAN test[/link], although RPM numbers are hardly mentioned.