Aricado - This one is a multisystem, abandoned last one as I was getting a lot of cross-talk and interference on the wiring, also the two case halves didn't stay together securely. This is MK2 (and hopefully final!). No-one else seems to have tried such an interchangeable system before, even on BenHeck; so my project is unique.
TimmyDX - I prefer the "gently does it" approach. I get the sides very straight indeed and smooth, as I finish with straight sanding. I also have steady hands and am able to cut in straight lines. I don't have access to a CNC machine, anyway, a lot of the casing has to be made my hand anyway.