Update;
I have completely dismantled and examined the Ryobi 30. The transfer ports are similar to Stihl, the new piston uses steel rail rings (less subject to ring flutter at high RPM), the new crankcase has a wider flange to accomodate the new ports but the bore is still the 25cc pattern. The tuners will have a ball with this one, the transfer port area is probably twice that of the old one but is blocked at the crankcase flange. The ports can be extended into the crankcase so they can flow from the bottom as well as through the piston. The piston windows have sharp edges at the entrance and can be contoured to improve flow. It will be interesting to find out just what this engine is capable of. The port timing is very mild and there is a lot of room for improvement. The stock muffler is packed with wire so there is no open chamber. I don't think the new cylinder can be used on the old crankcase without chancing leakage at the ports. I did not mike the bore to see if the pistons are interchangable.