Thats a pretty conservative setting(30* total). I've been asking total timing questions on this board befor it went down..over on performance boats ...everywhere I could. The best answer I can give you is that there are a lot of different variables that will effect your timing. Altitude, open chamber heads vs closed, cam profile, fuel type, compression, ect . Personally I think 30* is a little too conservative, but too conservative never blew up a motor. Others may or may not agree with me but I'd bump it up a couple of degrees at a time while gps'ing until you hear detonation or no longer see mph gains, and then come back down a couple.