Thats a pretty good summary JIMARRINGTON. See my .02$ below.
Second, getting a good seal on the piston is important to seal the exhaust out of the crankcase as exhaust into the crankcase dilutes the fresh fuel charge. Not to raise the compression. So a Bowman ring is a good thing to have.
Perhaps it is a benifit in both regards, blow-by and compression. The stock single ring has such a huge end gap that I'll bet compression is suffering, and compression is torque as they say. The later model Ryobi's with the two ring piston has perfectly fine sealing rings as is. No need for a Bowman or any other ring on those.
Fourth, the transfer ports are good as is but if more scavenging is needed for more power, the best machining mod that can be done on this engine is to increase the area of the exhaust port. Not the timing.
Increased exhaust area can be gotten by increasing the width of the port, the height of the port, or both. It happens that if you increase the height of the port you also increase the duration (timing). This provides not only a larger cross section area of the port but it's also open for a longer time. This gives a greater value in the "time-area" calculation, from both area and timing, and gives even more exhaust flow than would if you just increased the projected area by increasing the width alone. I don't really agree that the timing should not be changed.
2. Get a 10 to 11mm carb to match what the engine can draw from the intake reed.
av8tor is using a 11.1mm venturi carb, combatpilot and diceco are using a 12.7mm carb. I'm not sure what others are using. I may have missed something but I have not seen any performance results for a Ryobi with a 10mm carb.
4. Switch to electronic ignition so that the spark can be dialed in optimally. Not to mention making it easier to start.
From the recent work that combatpilot has done an electronic ignition will not give any better top end performance. 28-30 degrees advance is pretty much standard for these motor it seems. combatpilot has measured this with the stock ignition. This means that there isn't much if anything to be gained by the ability to "dial it in". The electronic ignition sure does make it start and idle nice and it's a bit lighter but it's pretty pricey. Your $50 Ryobi project just doubled in price at a minimum.
diceco