Never used nitrous; can't afford the learning curve......that said I would regard the 2 plates as approximately additive and I would jet each plate as a stand alone, I think that would be the most conservative/safe installation
I used to spray 200 on hyper pistons and 87oct pump gas, got me 5.70's in the 1/8th. The most important thing about that learning curve is not to over time the engine. Too much timing gets you detonation, that's the big engine killer.
2nd most important thing is to make sure you are on the lean side of max power. If your tune-up is fat and timing adjusted to get the most out of that fat mixture, you will then have too much timing and hurt parts if that fat mixture gets leaned out for whatever reason.
To stay out of trouble, rather than adding timing to see if you gain mph (which could get you into detonation), a safer approach is to first take timing out and see if you lose mph. If it does go slower, at least you know you were on the safe side of ideal timing. Same with the mixture, keep taking fuel out until the car slows down, then add just enough for max mph. Lean is mean and won't hurt a thing, but too much timing with nitrous will cost you some pistons and maybe more.
