I want to know of anyone has any tricks to stop or at least minimize the warping I'm getting when I make molds out of isophthalic polyester resin, Vinyl ester tooling gelcoat and 1.5oz chop strand matt fiberglass. I'm having some trouble with milti piece molds perfectly lining up and flap panels curling up. I recently laid up a flat panel on a piece of thick glass. The next morning the glass was bowed a lot. The fiberglass released itself from the glass as the fiberglass panel curling up fought the glass wanting to stay flat. This was a wet layup and I used no heat. I laid up 2 layers and let that cure. Then I laid up 3 layers letting that cure and then another 3 layers. My molds are always 8 layers of 1.5ox CSM. I usually put a fan on the laminate as it's curing to keep the heat from raising too much. The same kind of thing is happening on 2 and 3 piece molds for motorcycle fairings. The halves don't line up perfectly most of the time. My molds end up going into an autoclave at 210 degrees F at 40psi so I cant' use wood to back the molds up. 

Would vinyl ester resin fix this problem totally or partially or would it not make much of a difference from isophthalic polyester resin?