From Mahle Tec :
Mitch,
A properly tuned 300hp nitrous system should be fine. These pistons use 2618 alloy forgings and will hold up to a fair amount of abuse. As you mentioned detonation is a piston killer and as long as you stay away from sustained periods of it you should be ok.
Best Regards,
Trey McFarland
MAHLE Motorsports, Inc.
I think I'll keep them and give them a whirl - the larger dome pistone like the ones I have are the 2618 alloy - many others are not,,,,,,,