making cover for my fiberglass boxes

Hey all, trying to finish up my trunk install. If you look at my sub enclosures(link in sig), you can see that the front of the enclosures have a curve to them. What I am trying to do is make a cover for the front of the enclosure that is about 1/4 to 1/2 inch thick (the piece would only be covering the front part which is below the height of the sub). Seeing that it would be hard for me to cut a piece of MDF to follow the exact curves of the enclosure, I made a fiberglass copy of the front piece. I was thinking of using fiberglass to create the top edge of the piece (think of something like the top of the door panel, the part that gives it the depth.) What would you do from there? I was thinking if there is anyway to just fill it in, but I don't know what to use. Are there any products which are fairly inexpensive that can create that much thickness (I don't think that stiffness is a major issue since the fiberglass plate I made is pretty stiff already, and its only a cover piece anyways). Maybe some kind of expanding foam that I can shape easily, or anything else that does the same? Sorry, I am really inexperienced with this type of work, and I couldn't find any info about doing this. Any help or other suggestions are greatly appreciated.Jon

Don't like rockford subs? Then don't look at my car =)

Go to homedepot and theres a filler foam for walls and stuff called like FOAM something. just build that up cut it down with a razor and sand.dream it, build it, fiberglass it

i would try duraglass.... or as i like to call it "Hairy Resin"     It is f/g resin, presaturated with fiberglass strands. It can be used thin when fresh or you can let it cure a little till its gel like and sculpt it like clay.   Remeber to wear gloves, this stuff is messy like you would not beleive.... have fun