Here is the Bass Knob mounted on the GPS Bracket. No holes in the SS. Also I was able to run the wires for the knob hidden without taking anything apart. Nice.
The down side is my Discus Amp required a LOC from the SubThump BA harness. Along with that I had to run my Amp signal to the front of the car and back through the knob. So the bass is a little muddy, but plenty loud.
Here is the knob mounting: