I hear ya. I am in a very similar boat myself.
What did you use as a mould sealer?

Hanaldo (13/06/2017)

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Gelcoat would bond fine, but it wouldn't be the easiest thing to get a smooth surface with.

I agree, and it is a real pain to sand too, but as I have mentioned, I am looking at all possible options at this point.
If I can find something that works well, and does not cost a fortune, that is what I will be using.

I am in Australia, but I do know where I can source Duartec products and have thought about using this, if all else fails.