Yes that foam looks really handy, so you won't need to bulk it up too much with the fibreglass I guess. Such messy stuff, the resin is so annoying when it gets everywhere. My error was getting the odd resin drip on the bumper which I thought would chisel/flick off ...nope! Lol. Lots of sanding down.
I'm pretty sure I've cheated before aswell and used that glass reinforced filler for bulking which sanded pretty well but needed serious skimming afterwards.
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