Ops, I forgot to post about the AFR mount bar thing. So I used the scrap piece of fiberglass that I cut form the back of the rectangle box I made for the EBC. I made trimmed the plate to fit snugly into the slit that I cut into the side of the coupling. I eyeball cut space for the wires so the AFR gauge could but up against the coupling.
Once that wire part and out of the way, I used the grease/toothpaste trick to get an estimate of where to drill the holes for the mounting nuts. You just dab a little bit of grease or toothpaste on the end of the mounting screw while they are secured in place. You then carefully lay the unit into the surface you plan to drill or cut and then lift off. The grease/toothpaste will leave its mark on the surface. This is where you cut or drill. The toothpaste was hard to see so I put 2 small dots for you to see.
YzGyz