Hi Bill;

There is still a debate as to the probable cause:
Folks are dancing around the possibility that some of the o-rings out there may be too big to start with, and under temperature and combustion pressure, they expand, leaking coolant.  Read some of the reports here (some are professional builders):
http://www.nopistons.com/forums/Review-Rotary-Aviation-t67208.html

People have driven for year(s) with minor leaks and no ill effects.  If it overheats a bit - coolant can pass the orings without apparent oring damage - not completely a bad thing - you just burn some coolant. Sitting, it will rust.
Enough coolant to stall the engine or prevent it from starting puts you into the next category.
When in doubt, stick with OEM bits.

On an aside - Tracy mentioned plugs - who is using old 4-prong vs the RX8 thin wire plugs.  The old 4-prongs have been reputed to cause cracks around plug holes.  Note that the RX8 have moved to single thin wire plugs.

Cheers
Cary