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Dougy, probably best to talk to manufacturers regarding plug spec. Too hot and can burn holes in piston crown, too cold will oil up. Plug temperature is fairly critical on 2 strokes.
As a long term motorcyclist, back in the day I had a Yamaha RD200 that would chew through the better quality Bosch plugs in a couple of hundred miles where the NGK's would last a couple of thousand.
Sailed in a boat with a Dolphin it never missed a beat and started in reverse every time.
my professional experience with them other wise was that they were the most useless lumps and to be avoided as neither we nor the customer were happy at the bill to sort them
The difference was the engine was taken out and at least the electrics went back to the factory ever year did not stop me suffering every time we changed direction or went to start it