I have much appreciated the comments and help regarding replacement solutions for the above-engine compartment.
This fall and winter, I plan to implement Pierce Stewart's recommendation to use Hardiebacker board to create a noise dampening and fireproof environment above and around the engine compartment. However, my coach is currently in dry storage, where it is difficult to work, and a temporary fix is called for.
So I am soliciting opinions regarding the use of 1. Barymat in the roughly 2-inch deep "Box" above the engine; Barymat is a 1.25-inch thick sound-suppressor product, not fireproof.
I would then afix Heatshield Products 0.25-inch mat over the Barymat. Heatshield Products IS a fireproof mat for engine compartments. I would then seal around the edges of the box with silver tape.
Any suggestions, cautions, or critiques of this idea will be very much appreciated!