Calculating odds of hitting one of several points before a 7

So years ago I read the Doey-Don't system with the 5 count. I always played it by backing up with odds on the come bets and pass line bets. As I ahve matured, though, I have come to appreciate the slight mathematical advantage of laying odds on the don't pass and don't come bets instead. What I can't figure out, though, is if I end up with three don't come bets with odds, is that too many numbers to have playing to make it worthwhile or should I stick to the come bets?
Basically, what I am asking, is there a way to calculate the maximum number of don't come bets to be playing to make it more likely to hit a seven than ANY ONE of the don't come numbers?