The poor old pressure plate was not coping with 13psi. I hate to think what would happen if I keep it in with 16psi!
 

Once again a local special from RES (Rotary Engine Specialists) of Auckland. They get these made up using standard Mazda parts with a heavier duty spring material (I think). Any way, it holds on a lot more, and the clutch feels not too much heavier. I chose to keep the standard plate, to keep the derivability. A good compromise.