Just an update! Cases are coming together real soon.
The prototype front panel arrived... holes lined up perfectly... and most importantly, the gain marks line up PERFECTLY with the 12-step Grayhill selector switch.
Next step is manufacturing a prototype for the rear panel... but this should be easier than the front panel, since the dimensioning and holes are not as critical.
BTW, this is a (4) channel preamp case in 1u rack height.
I'll also be making an (8) channel preamp case in 2u rack height too.... that will be later.