Engineering and Boost

Just a little discussion while I dream of fantasies at work...

My main question is what amount of boost (psi) do you feel is safe and at what amount of boost do you feel the tacoma v6 4.0 would pop.

Info to consider....
Stock internals
Toyota manufactures the supercharger kit, with the pulley upgrade I hear it is about 8 psi.
8psi = load X on motor.
Does 16 psi = load 2X (linear) or is does load increase exponentially with boost??

Most design applications require at least a factor of safety of at least 1.5. Therefore would that mean at the 4.0 (stock) could support 12 psi MAX (linear) or if exponential is would be less than 12 psi.

Or does that mean 1.5X ? which would be different than 12 psi if exponential ?

If anyone has a boosted taco and you have run some numbers chime in !
Thanks