You could also look at stripping to the metal and putting in Lizardskin for interior heat shielding along the firewall + footwells (+ grip tape where appropriate), and then use reflective foil on the "outside" of the firewall to keep some of the engine bay heat out.
Also while googling around on the subject, I found this post/thread to be pretty informative, has some neat info on overengineering with Aerogel mats:
Lizard Skin vs. Second Skin vs. DynaMat or other- Which did you use? - FFCars.com : Factory Five Racing Discussion Forum