Actually, I'm playing at sea level right now...

I machined out the squish band, and left out the base gasket completely, using only Yamabond sealer as I often do. This raised the compression but of course lowered the exhaust timing. I raised the exhaust port to get it back to 150 degrees timing, but left the transfers alone. I've done this on a lot of engines with good results. There is something I did forget when I got into a rush there at the last, and that is to check to see if the hole in the carb mounting matches the carb opening. If there is a lip there caused by the adapter being smaller than the carb, that could cause some turbulence and hurt performance. Also, when cleaning the plane up I see there is noticeable black residue, so I'm sure the ring still hasn't seated, though the Bowman rings usually seat very quickly.

I'll run it some more and get the ring seated and mixtures re-dialed in, and if it doesn't pick up I'll pull it off and check that carb adapter. I did raise the reed stop as you mentioned. Also, the comparison I made to the Echo engine... it is spinning an old Top Flite wide blade wood prop over 500 rpms faster than the Ryobi with a Top Flite Power Point of the same pitch and diameter. I really like the APC props and use them a lot, but these in these two cases; a Fokker Triplane and a Tiger Moth, the wood prop just looks a lot nicer.

Thanks for the ideas/help,
AV8TOR