40s on small can exhausts and fifties on in cowl exhaust DO run at or close to 7000 rpm -
which props used in these tests IS important --
these were Bambula 20 x10 props and at 4500 ft elevation on other props with narrow blades the rpm is typically higher .
For what it isworth - we ran ST2300's on 25/30% nitro small tuned exhaust and 18x8 APC props -these turned over 9000 and pulled like a freight train - but at 16 bucks a gallon -I finally threw in the towel - 7 flights per gallon
that's over 2 bucks a shot.
Low nitro - 1.6 setups are a lot less expensive to run -and are a better way to go but here at 13 lbs - they just would not do the job - close -but no cigar --