RE: Valve Screws - Suggestion for a better design
I've got a pretty solid plan for you that I noticed the Real Wind folks using on their rentals in the Gorge. They have all their boards fitted with Chinook's two point plates. Once the day is over and they are packing everything up, they remove the plugs and insert them down in the hole that the universal attaches to, and then they move the retainer mechanism to a closed position capturing the plug. Until the plug is removed, the universal can't be installed. Really, a fairly sound plan that leaves little to chance.
For myself, I follow geo's plan and never remove plugs unless I'm travelling by plane or through higher elevations. Never a problem this way, but I should note that I carry everything in a light colored van. Also, most of my white boards are stored in insulated bags that further mitigate the affects of elevated temperatures.