I would suggest you do not do that. Long after the plug has been removed Polyester molds will still be reacting. They shrink and twist. None of my epoxy molds have done that.

I use mat with epoxy with no problem. As was previously stated screw up the mat before using it makes it soft and pliable. Or separate the layers and apply. Mat will soak up a lot of resin be it epoxy or polyester. The size of your mold will quite easily use a 1/2 to 3/4 gallon of either resin.

Ed S