Rufcut thats not a stupid question, its is a very astute one and the answer is no you do not have to double nut the small two strokes and they can also use the all plastic spinners. Using all plastic though the normal precautions must apply and their can be no contact betweeen blades and the slot and yes you can dremel trim the slots by hand.

Those engines are not subject to the same pounding in the plain of rotation most four strokes are.

I do as jetmech suggested and use the sixty size as my personal limit for the use of plastic spinners on two strokes and not at all on four strokes.

John