Ok, I was wondering if the fiberfill or an epoxy would work better for holding the dowels ect. I would almost want to do some sort of metal reinforcement, pop rivet it, bondo\fiberglass. I think this would add a bit more strength and rigidity.
Not a bad job for your first go at it. Kudos for trying something new to you!
I was wondering how people mounted the radios behind the bezels. Did you just use some standard l brackets from the hardware store? Do they make an actual mounting kit from another car that will work?