please see the enclosed pictures, which are modified from colin's original v1 build instructions.
in the picture of the interior view, I have marked the three IDC connectors associated with the pot & main step-switch boards; with the 3U panel, these boards sit a lot closer together & so the orientation of these connectors is important. in this picture, everything will be fine, but in both my factory machines, I had to replace right-angle IDC connectors (i.e. not like the ones shown here) which would otherwise have prevented the connectors being inserted.

the second picture is of the mode switch board. this runs the full height of the panel normally, & therefore needs to be trimmed down to fit behind the 3U panel. my markings are approximate; this is a tricky part of the job, since if the board is mounted even slightly misaligned, the buttons will foul the panel & get stuck when you press them. I found the best thing to do was mount the switches in the board & offer it up from the rear of the panel before marking the positions of the new holes. also, make the holes slightly larger than they need to be, & fit washers on both sides of the board. this way, you can adjust the final position of the board so that everything works.
I scored the board before trimming the excess length in my first machine. the second time, I just went for it (carefully!) with my wire cutters.

there's space on both versions of the 3U front for you to add the name of the sequencer (see the pictures of mine in the photos section). I would recommend also to change the colour of the inking on the red acrylic panel to something other than black; it has turned out to be quite hard to read!

you can change the colour of the aluminium version, but not the acrylic (a schaeffer thing, this), & the text or font or colour of the labelling on either.

the two small schaeffer files are for the panels I used for the sides, top & bottom of the finished case. the top & bottom are very thin & bendy, & need additional support pillars attaching to the back panel (not shown). also not shown on the back panel are the mounting positions for the main PCB & the holes for the midi sockets & power connection/switch. you may want to experiment with different positions, depending on the length of the interconnecting cables you use.
the case is completed with the purchase of a set of "housing profile 1" corner pieces from schaeffer. the bolts that go through the front & rear panels into these corner pieces are not self-tapping, so I used some spare M5 bolts to cut the necessary threads in them. 

hope this is useful. let me know if you embark on a 3U version!
duncan.