I have put the stunt venturi in the (early) combat version and gotten a pretty good run for stunt with 2 extra head shims. Tommy Luper used to fly a profile with one, too. They didn't *seem* to be as highly timed as the later ST Combat 35s.
I would stick an PAC 10 1/2 X 4 1/2 on it, 5% nitro 25% castor fuel and go.
Bill <><