Case to house dual rail adjustable PSU

[Aethelstan]

Hi folks. I have decided to make a dual rail PSU, I have a decent grasp of the electronics side but I am struggling to find much regarding how a case would be specified. There are lots of project boxes to choose from such as aluminium, plastic or a combination of the two, and I can 3d print something in ABS if needed. Obviously if I were to have any exposed metal then I would have it earthed, but would I be better off having something completely plastic to avoid an earth, as in  class 2 device? My feeling is to use/make a plastic box with a sheet aluminium plate at the front and rear, both bonded to earth, but that's based on a gut instinct rather than any concrete data or theory. On a related note, the toroidal transformer I have for the project has a metal bolt to mount to the chassis. If I were to go for a totally plastic case, could I use a nylon bolt instead?

[CopperCone]

Easier to make a metal box then earth front and back with a wire so long you use star washers that dig into the metal.
 Metal will also sheild external emissions and supress internal emissions.

[David Hess]

It may be possible to use a metal enclosure as the heat sink for the power pass elements if required.