Does anyone have any thoughts regarding positioning on defense (-1, +2, etc)?  I've followed successful coaches over a period of time and there doesn't seem to be a pattern connected to long term success.

I have a positioning formula that I use with zone and press (I've never run a team with man defense). I won't post the formula specifically because, the act of doing so would then render it meaningless as opposing coaches could game plan around the positioning. 
 
Opponent's rebounding, LP, Per, my choice of defense, location of the game and opponent's likely tempo are all variables taken into account.