ILO64 and Doug,

I installed them when the head got loose - I think the o-rings compress and other parts stretch out from all of the pressure of flying (and crashing, and crashing)! I inserted them directly up against the O-rings in pairs of 2 to start with, then ended up with 3 or 4 (can't remember -they've been holding the shape for a while now). Just do not put them on the stepped side of the existing washer- that is reserved to ride directly on the face of the bearing.

Cheers