RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
I run mostly APC props, but a Zinger is what happens to be on my Ryobi at the moment.
Before worrying about other methods for stuffing the crankcase, I would make the bearing/seal change and see if the engine responds well first. You can't move the backplate inward on the engine much because the reed valve stop will hit the crank pin.
Once again, with the ring gaps you are running you would see a nice power gain with a Frank Bowman ring. 12 bucks isn't that much in the grand scheme of things... (Just my two cents here.)
AV8TOR