It occurred to me that I already have a supply of enclosures into which I can mount my synth modules. I have a few surplus of these steel boxes into which my father used to mount his electronics gizmos. I've pulled out his old wiring loom and this leaves me with a box with an aperture about 100 HP wide and 7.25" high. Not exactly a standard synth module size, but I can work with that. A bit of extra height (over the 5.25" eurorack format) means that my modules can be a bit narrower.
I've done a first mock-up of the panel layout for the VCO, and it looks quite sweet if I'm allowed to say so.
My next concerns are two-fold: How to mount a threaded strip top and bottom into which to fasten the modules, and how to arrange a power bus and fit in a PSU ? There's options here, but I haven't worked out the details yet.