It does have small feet that would cause problems, so the parallel
sounds like a good idea. Is the opening facing me for visibility or is

there more to it?

Visibility and convenience. I've tried the methods other posters
suggested and use the angle block and plywood for larger boxes but for
the small one you have a 2X4 spacer in the box should be enough. You
need to see that the wood doesn't touch the lower corner of the box
when you tighten the vise, and it's easier to add a C-clamp or 2 for
extra stiffness near the cut when you can see the upper edge of the
wooden block.

I generally saw/nibble/plasma a large opening in the chassis and make a
separate bolt-on control panel out of 0.062 aluminum. Flat panels are
MUCH easier to fabricate. Make sure the wired panel will pass through
the hole.

jw