There never has been a magic number, nor will there ever be, because the same circumstances exist today as when we lost Scott, that being If everything works properly on the cars, the fuel cars could run 1/4 mile right now. But if things go bad, and there are certainly many levels of going bad, there is a possibility that no track is long enough.
The same weekend we lost Scott, Fuller got stopped after a full pull with no chutes, while 5 years earlier Super Gas racer Phil Burghard was lost at St. Louis after going off the end of the track. It doesn't matter from which side you look at it, you can't get there, not even today. Scott's car blew up at essentially the same spot of the track that we're now running, so the track distance really didn't factor in, just like in Burghard's incident. When you have catastrophic failure, anything can happen regardless of shutdown length.
This sport is dangerous enough competing in the slowest of classes. Throw Pop in the tank and all bets are off.
Sean D