I used a dust cover for the whole pattern and then cut it in to two and reduced the metal I did not need with the plasma cutter, then I traced around with the plasma on 2 sheets of 2mm steel and then plug welded through and linished back to flat, now I can put one bit in from above and 1 from below and remove it if I need to get to the clutch without moving the whole box too far. This gives me around 6mm of spacer bringing me back to the 450mm / 451mm to match MKs measurement of his box.