I used 1/4 inch Dynaliner (from dynamat) under the front seat/floor panel, side panels and the small panel between the seat and seat back. I then used foam weather seal tape to seal off the seat and seat back. I use heavy foam and dynaliner to seal off any other gaps where hot air can enter the cab from the engine compartment like around the seat belts. This took a long time but it was a rainy day and I'm glad I did it. It has kept the heat at bay AND made the cab quieter as the Dynaliner is a sound insulator too, plus its water and oil resistant. Be prepared to take your time if you go to the effort of doing this as there is a lot of cutting and fitting. I have a glass windshield, hard rear panel and hard doors so the cab was getting a little noisy as the engine noise had no place to escape but the liner really helped out. I used 2 boxes of 32' x 54" liner to complete the job. Even though the Dynaliner's adhesive backing is pretty tenacious make sure your surface is clean and warm before adhering. And don't buy the cheap stuff just to find it came off a few months later.
