If you are using an IR gun to measure your temperatures, on that aluminum and otherwise silver materials you may not be getting accurate results. IR guns are calibrated for a black, flat finish and shiny, reflective finishes throw them off a lot. I'm convinced that the benefits in radiant heat reduction everyone thinks they are getting from silver, ceramic coated headers is just due to the inaccurate IR readings they get off of it.
If you are looking for an under carpet insulation I really liked EZ Cool. It's only for thermal, it's very light weight, and it's not expensive. It doesn't come with an adhesive side so it would have to be put down with contact cement unless you just install a piece loose under the seat area and let the seat bolts and carpet hold it in place.
http://www.lobucrod.com/faq.html
Good luck.