Just a thought passed through my mind.
I run the Century Freestyle with the plastic tail gear box and high speed metal gear set. at the end of each day of flying, i always inject fresh grease into the box to replace what was thrown out during flight. ( i use a mini grease gun with a needle tip, and #2 lithium grease cartriges). i just have a small set screw acting as a plug, i remove the screw and inject the grease.
but if we were to use sealed bearings, and silicon the gear case halfs together. would it be possible or even better to run oil? then the oil could be sloshing around constantly coating the gears. as with the grease, if there was not enough of it, it would simply fly off the gears and stick to the sides of the case.
Just something to think about....you dont see many car trannies running on grease...