Karl,
Go watch my gelcoat vid on youtube. Occlude o2 with plastic or PVA or whatever. If that doesn't work, the gel is old, notorious at big box marine because hardly anyone that knows how to use it buys it there. You can spike old gel with a few drops of cobalt, if you have any of that super toxic stuff laying around. Most people don't.

Go up to your local glass guy and have him pour you a quart from his drum. have him mix in a little Duratec Clear.


Hope that helps.