it' not the boost that's gonna kill you, but either the torque the motor is making or knocking from a bad tune.

Cylinder pressures are at their max at peak torque if you have a good tune. The higher the torque you make, the better chance you have of lifting the head. Just about everyone has a boost gauge and it's an easy thing to reference compared to a dyno to get torque figures, but be careful when just referencing boost to determine how much is safe for stock bolts.

If you are knocking, cylinders pressures will be far, far higher, and that's when you really need to be concerned.

 

50 psi and 22 deg of timing and the head will come completely off

 

I saw a video on youtube.com with AL tuning a car pushing it really hard on a Green Turbo I believe.