I remember seeing an article on this recently, though I don't remember where. It was in one of the RC publications somewhere, so I'm guessing there is research going on with this idea.

The upside to composite pistons and sleeves was that you wouldn't have to break in the engine any longer and that you could run the engine much leaner. The composite piston and sleeve would handle higher temps which would allow the leaner running engine. This would also create much more power, higher RPM's and longer run times (due to less fuel used in the leaner engine).

The question is will they be durable enough for the RC environment and will they be cost effective?

I hope so....