I have put many an hour on my converted Saito 91. The leanest oil ratio I could get away with was 22:1 and not because of the rod bushings. There is plenty of oil in the case to keep the crankpin and wristpin bushings lubed. The problem is the exhaust valve guide. There is no oil traveling up to the rocker boxes from the crankcase, all of the oil for the exhaust valve lube comes from the exhaust gases. If you cut the oil ratio too much there isn't enough and the exhaust valve will stick in the guide. Been there done that. The exhaust runs much much hotter on the gassers and it tends to dry the oil off the stem and guide pretty quickly. I made it a habit to pull the two screws and take the rocker cover off after each flying day and drop about 5 drops of high quality synthetic on the valve train and put the cover back on. Never had any more trouble after going back to 22:1 and lubing after flying. I was trying to run at 32:1 when the valve kept sticking. There are really no drawbacks to running the extra oil except the cost. Plugs (I was running the RimFires) lasted an easy 30 to 40 hrs and sometimes more. Good luck with yours.