I would build a good mdf box and fiberglass the inside of it- You can use as much or little 'glass as you want- and if it's ugly it wont matter. I'd just glass all sides and make some fiberglass 45s in the corners. You could put some wood in the corners and just 'glass over that. After you get a feel for how long it takes for things to set and working with the materials I'd move on to something bigger.
A box with a fiberglass face or entire box with just a wood skeleton. I'd just play with it and get some practice.
well thats what I was thinking of doing, because my car is so old. like where there would normally be a holder for change, CD's, etc. theres a tape holder.
but its funny because the car's stock radio didn't even HAVE a tape player... plus it looks really ugly so if i fiberglassed it it would be slick... maybe put a little 6x8 in and 2 tweets on either side of it???