Without sounding like an a**, whatever anyone here thinks is really not important.
The people you need to be asking are those that have done it, and considering that I can probably count those people (person) on one finger, I would venture a guess that the only person you can ask is yourself, after you've blown a motor.
Now I'll turn the smart a** in me off. 6 or 7 psi might be good, but you got to make sure that the motor is not knocking. Detonation kills the motor. Run enough fuel and pull the timing enough and ANYTHING is safe until you pop a head gasket.
Contact either Apten chips, Jerry from Ford Chip, Bob from Diablo, or Alberto from the company who's name I can't remember.
I hope he chimes in.
I'd be curious to see if Alberto can implement a knock retard parimeter into the EEC allowing it to display not timing advance, but timing retard. A real time, data logging device like an Autotap is also essential.