Ignition Advice Please

6 is fine on most applications. We have an 8 sec nitrous car using a 6 with a grid controller for well over 10 yrs without fail. i also have a digital 7 thats been running for many years street strip 14:1 Nitrous car as well. Latest build has the grid ignition and controller also nitrous 13;1 street driven. These three are BBM nitrous cars that are making over 1K hp.