Thanks for all the feedback. It's helping educate me...
Man, designing the circuit and PCB is the easy part. Picking the right case, and engineering everything to fit and work together is the hard part. (It always has...)
Using the blue case, I tried drilling XLR holes on the side. Surprisingly... it was easy to drill 15/16" holes. I used my trusty step drill. The problem is drilling the 1/8" mounting holes. They fall exactly on the curve ridge of the case... ever try drilling on the center of a convex surface? The result was misaligned holes and which makes the XLR jacks crooked, which involves more work straightening it out. I emailed the factory to see if they will do custom mods for me and have them drill these holes for me! If yes, that solves one problem.
It took me HOURS to do these holes... but I was also figuring things out and trying different things. Compare that to 2-3 minutes milling the rear panel with my CNC!
I'll probably create a drill jig/template with my CNC and use that jig when manually drilling the case, see if that makes the manual process faster and more accurate.
An option I'm thinking is doing 2 versions... and charging more for the XLRs on the side model to justify the added labor that's involve. The XLRs at the back will be priced cheaper.
As for the stepped gain + trim VS. pot control... if I'm going with the pot control, I need a special kind of pot with my circuit. I need what you call a Reverse Audio Log Taper. Not a Linear Taper, and not a Log taper, but a Reverse Log taper! It's a special order item and I asked my sales person to give me a quote for these special pots.
Personally, I still prefer the step gain + trim... but weighing on the cost compared to pot control, the pot control is attractive... but since the pot is a special order item (i.e. expensive), I may just use and go back to the original plan of gain + trim.
Okay, photos of the blue case with the XLRs mounted on the side.
Again, the front panel layout is not finalized... still playing around with it.