Thanks guys,

I've checked the clunk and its definitely where it should be. I've also checked the pressure line from the muffler and all appears to be clear. As far as running it slightly richer - Its already slightly rich (not much) and don't think I want to go any richer at the mo.

I've had the problem with it quiting since flying the model for the first time (maybe 15 flights ago). Big fast high g loops are no problem, rolls, inverted flight - no problem - its only when I try a flick roll or apply reasonably abrupt up elevator to enter a spin does it quit - and when it quits, it quits - just stops immediately.