Looks like the Twin ARB compressor should fit then as ARB says the dimensions are 4 x 7.5 x 10.8.A review of the instructions indicates that the heat shield will wrap around the exhaust pipe between the muffler and the cat.
My VIAIR pumps are about 10" long, they will fit side by side in the cradle, and they utilize the majority of the room. I have the VIAIR model 20020 with Dual 444C compressors. I am not familiar with the ARB compressor(s) you have, there is about 12" of room between the 2.5 gallon tank and the end of the bracket.
Thanks for the pic @Koloradokid. So am I to assume the muffler itself doesn’t get hot, and it’s just the tail pipe that does? I think I’d prefer to get some more of that stuff and place it along the side of cradle.