It's not that MDF is that expensive but it is more expensive than a lot of other woods and I have a lot of plywood around our shop so I thought maybe I could use that. Somebody told me that it doesn't really matter what kind of wood I use as long as I make enough ribbing to make the frame strong enough to hold up against the curing process. As far as making the supports, I thought that I could just use wood glue to hold it all together. No matter what kind of wood I use, should I use some type of screw or T nuts to secure the frame together? I don't wanna "floppy" dash, so if I have to screw it then glue it thats fine with me. Also, I'm putting in a set of speaker rings for a 6 1/2 inch component system in the dash, and so I want to make sure that the dash is as sturdy as possible. Appreciate the info.