I uploaded a couple of photos to this group last year that show just
these two simple modifications (link below). I've mounted multiples
directly on top of the rails at the top and bottom of the suitcase; I
didn't even drill holes, just used a couple of wood screws and screwed
them on. Super easy. The mult module doesn't need any space behind
it, so it works fine.

It's also very simple to cut a small hole in the side of the case, and
drill four holes for the screws, to mount the mains input inside the
side of the case. (And Stu, I do sometimes use the on-off switch for
'waveshaping', so to speak...)

photos:

http://launch.ph.groups.yahoo.com/group/Doepfer_a100/photos/browse/c8bf