Well, besides the obvious answer, gas tank. I had to pull one of my tanks due a leak. The tank is fixed. Now, what to use to replace that horrible fiberglass insulation? My plan is to double layer Eastwood's Thermo-Coustic material along the inside walls of the enclosure. This material is less expensive than the comparble Xtreme Dynamat, and appears to offer the same benefit of protecting the tank from the engine bay heat. Ethafoam looks to be a very strong candidate as an intermediary between the tank and Thermo-Coustic insulating material. Flash point is a 600 F. It can cushion 2.5 pounds psi., is very light and can be cut to contour the tanks. It is closed cell, so no water/moisture absorption issues, impervious to most chemicals. Lastly, it has passed the FMVSS 302 flamability testing. The Federal Motor Vehicle Safety Standard (FMVSS) 302 for flammability of interior materials - [Passenger Cars, Multipurpose Passenger Vehicles, Trucks, and Buses] is one of the most common automotive materials tests. Ethafoam 220 appears to pass all the criteria requirements. What does the collective think? Not trying to re-invent the wheel, just want to keep things right and safe. Thanks in advance for comments and suggestions. Ciao, George