Hi mate,
I'm new at this forum and couldn't resist to give you a reply!
Before rebuilding my current engine i used to run my cossie at 25psi with the standard gasket. I don't agree with the idea to let the gasket to fail!!
It could result in a whole disaster, if the gasket fails from a waterway down to the chamber, therefore it could result in water pouring down the piston, this could damage the piston surface and much more worst it could result in a bent conrod!!!!!! and i think that you don't want this to happen.This could result in a whole engine rebuild an would cost you grands!! My advice is to lift off the cylinder head and replace it with a group A item just before it fails. Better safe than sorry mate!