Dynamat, extreme dynamat, and similar products that are a thin dense material with adhesive to adhere them to panels are more of a 'sound deadening' material than thermal. I think these materials do very little to nothing relative to thermal insulation (although the 'foil' layer will reflect radiant heat).
I'm currently installing thermal and sound damping material on the floor of my '60 Corvette prior to carpet installation, and I used pieces of 'dynamat' material on the flat sections, then covered the entire firewall/floor area with a foil faced, 3/8" thick wool-like insulation (similar to std carpet underlayment).
I've never seen anything in the aftermarket that is very similar in appearance to the factory-utilized Camaro floor/trunk material discussed here. Re the material used in the trunk floors (so very inconsistently) I wonder if perhaps dealers didn't install it in response to noise/resonance complaints from customers??... I would think if Fisher or Chevy installed it in the factory that it would have been done *consistently* at least...
