To Mahler one - I no longer dry mount gallery prints, but when I did I made sure the room was not humid, pre-heated the print and the board (one at a time) just prior to mounting, and placed under aluminum plates immediately after mounting. I made sure I left in the press the right amount of time, no more (I was told that if the board gets too hot, it stays hot after removing from the press and it can buckle for that reason), no less, for the final mount (25 seconds for me, MT-5 at 210F).
I never ever had a print buckle, and have many today (that were mounted in the late 70s through the 90s) that are still flat.