Did the trick!

I used a pair of RMP Backer Plates to mount a Quick Release Mount for a 2 1/2 lbs. Fire Extinguisher. Since I do not have the tools to cut threads, I found a pair of T-Nuts to fit the bolts of the mount and drilled the Backer Plates to accept them. The Plates themselves fit nicely in the RMP with just a minimal amount of wiggle room, but once tightened, are quite secure. The metal felt very dense while drilling through it, and if I had the right tap, I feel it would take coarse threads very well. They feel strong enough that I am confident that the lip of the plate will hold the weight of the extinguisher with no issues. Once drilled and painted, they blended into my RMP. They do sit a little proud of the RMP, so I added some felt to protect my leather seats.