1/2 way through my second year with my Ryobi conversion. The darn thing just gets better and better! Mine's in a kit build Stinger 1.20 with the short wing option.
I started with a Jag-converted model with the single ring and un-slitted cylinder on C&H ignition. Best prop was an APC 18x6W "fun-fly" prop @ 7750 RPMS.
Last year I got the urge to tinker with it, and swapped in a twin ring piston, a Walbro WT-433 carb with a 5/8" bore and 11.1 venturi, and I opened up the reed valve stop. Last years best prop was an APC 18x8W "fun-fly" prop @ 7550 RPMS.
I've got about 3 gallons of fuel thru it, and it's showing signs of overspeeding in flight... I don't think these motors like RPMS over 8k, no matter what kind of carb/muffler, the engine just doesn't flow air well at higher RPMS. Maybe with port mods, but I don't wanna go there!
I just put on a 20x6 Zinger and got 7100 RPMS max. I richened it up a bit, and Wednesday I'll fly it again. I'm really looking forward to this, as I have always felt that a 8 pitch prop was too much for the draggy Stinger.
With the 18x8, the plane had the ability to *barely* climb out of a hover, but with dangerously low reserve thrust. I'm really hoping the 20x6 helps me out here.