OK, i'm trying to reshape the bottom clamshell of my fiberglass gauntlets. They are a bit warped. I went and snagged a heat gun last night, heated the part that is warped up, shaped it to make it line up right and then ran cold water over it until it was cool again. 2 hours later it was back to it's warped shape. This is the first time I've ever worked with fiberglass. Am I doing something wrong? Any help would be appreciated.