I'm worried about excessive muffler heat on my Avanti's fiberglass floor. I'm looking at using a FlowMaster Super HP 2 ... 4" X 5.63" X 18" (because my LS2 needs an"old school" tone and moderate sound) which is designed (with packing) to "control heat transfer". Avantis don't have heat shields under the front seat ... should I be worried (also because of my tight tolerances from using a 4" thick muffler)? I have cast iron headers, Cats, 2 1/4" SS exhaust pipes, no H pipe (yet) ... and also plan on using 12' Vibrant Bottle resonators to help control the trailing throttle and drone. Anybody?