Hi Friend,

I once saw commercial panels being made and this was done by assembling a stack of SIPs and then enclosing them within a large plastic sheet envelop which was then evacuated of all air until the vacuum pulled resulted in the ambient air pressure (15lbs per sq inch) compressing all the panels in the stack.

Even if you do not intend to use this method you now at least know the general pressure level needed to ensure good bonding.

Regards

Ken Hume