Ive realised something tonight.
Cutting the -VE or +VE has a subtley different effect to earthing the -VE
BOTH methods introduce a random spark event in the cycle, but cutting them can ONLY introduce it in a way that gives extra RETARD and grounding can only introduce it in a way that gives extra ADVANCE.
So cutting the -VE or +VE is infinitately better than grounding the -VE (which is what the limiter im talking about does I believe, although ive yet to test it)