There is a version as EllisD says which comes with two rectangular holes set close together in the area of my 24 pin cable hole. Hopefully yours will have these, and it'll save you a bit of filing ! :sweat:
At first I tried a large dia. drill bit (approx half inch) and found even though I had scrap wood 'G'-clamped behind, the drill was causing too much 'trauma' to the Case, as it 'bit' through. (see: '11o'clock') in photo below. I decided to drop the drill size drastically.
At '7o'clock' you can see my first (and last) attempt with a 'cutting wheel' (or 'Dremel'). I can only speak personally, but in my inexperienced hands, it's only too easy to 'over-run' my 'cut', and the
vital eye-protection makes it difficult to see my 'scribed' line.
So I had to do it the 'old-fashioned' way, I'm afraid.
Scribe my desired aperture. Scribe an identical shape approx. 3mm
inside of this. Centre-punch at regular intervals, and drill a series of holes with a 4mm drill. These were then joined using, (initially) a rat-tail 'modeller's' file, and then the blade (only) of a 'Junior' hacksaw, before filing smooth. This worked particularly well for me, as I was making holes in some hard to access places.
I know they're 'archaic' but you may find the old 'ribbon' IDE cables easier to re-route and hide in the Nine-Hundred, than the modern rounded ones !
Cheers and all the Best
terminator