How much nitrous for a stock piston?

I have jets # .063 and .072, for nitrous and fuel respectively, I chose a .072 instead of .071 to richen it slightly for safety, in a small engine. I got the system from a guy who ran it on a stock 302. But I assume you are saying it will frag my 318, I can always go pick up a .055 for the juice and run the .063 on the fuel side, should give me 125, right? Or should I go down to 100?