I have gotten away with using 1/2" MDF for two tens if you brace it well. I also divided it into two smaller boxes to make it more rigid. The main things to consider are that it is the right size for your speaker and that it is sealed. One other thing is that if you have rear firing woofers...
I had a set of their cobra R replicas on my 95 and they were great. Never had any problems with them. I got the polished and wished I would have gotten chrome but other than that great dealing with them.
Clint
