Good work! I never went so far as to use Gordon's time/area functions on these little engines, but it is interesting. Gordon also has expansion chamber formulas in his book as you know, but there are now online calculators that you can use too. They are less cumbersome when doing "what if" studies...

On my Ryobi the prop is a Zinger 18 x 6. Mods are:

CDI ignition set at 28 degrees.
Aftermarket two tube muffler.
11mm venturi carb.
Standard cylinder with exhaust bridge and no ''slits''
Frank Bowman ring. (piston ring retaining pin modified) .000'' ring gap.
Base gasket left out; deck height .030''
Exhaust port timing raised to 150 degrees.
Reed stop set to .125'' (1/8 inch)

I was a bit surprised at how well it runs. An honest 8500 rpms with a TNC tach. It is in a big Tiger Moth biplane that rarely sees full throttle, but nonetheless I will put an 18 x 8 prop on it one of these days to bring the rpms down a bit...

My brother has a mild Ryobi in his "Ryan's Rebel". It has a 9mm carb, electronic ignition, gutted stock muffler with larger outlet, and it has the cylinder with the transfer port slits in it and no porting. It turns an 18 x 6 Top Flite prop at 7700 on my TNC tach.

AV8TOR