Update...
Right, so I temporarily put the frames back on the front panel so I can measure accurately.
The aluminium I got from ebay was bent using nothing more complicated than a couple of straight bits of wood and some clamps.....then I smacked it with a rubber mallet to obtain this:
Perfect fit......phew!
Dry fitting the back panel.
The motherboard tray will have to be cut slightly smaller to fit perfectly.
Then all the components will have to be flush riveted, so that the whole thing will slide in and out of the case. I will need to prime & paint the inside surfaces, unless I decide to polish all that aluminium.
I'm still worried about fitting the PSU I do not think the ATX style will fit and I want either a 1U or a 2U Rackmount PSU, but I'm not sure if they will be suitable for ATX.
A micro ATX would be better, but I don't think they will be 'beefy' enough for the job..
Decisions decisions?
I'm enjoying this mod, even though my plans are fluid, at the moment.
Ouch!