Today's update:
Disassembled the 900 totally, removing everything. Locate new cable management hole.
(picture from back side, easier to cut and grind)
Painted the whole cage flat black, like Antec now does with the 1200. Mounted the rad using 2 brackets on one side. Very sturdy, I don't think I'll put the other bracket in.
Sorry for the glare from the flash. One bracket is visible at top right of rad. Another visible on the table.
You can make out the res in the glare at top left.
Side shot, all wc parts mounted except CPU block:
I'm not too happy with my paint, it scratches very easily. But it doesn't look anywhere near as bad in real life as it does in that flash picture.
So, the loop's in place, case reassembled, leak testing overnight again. If all's good tomorrow morning, mobo slides in, PSU goes back in, and I have another oh sh** moment while I hit the power. But I feel a lot better having drained, moved, and reassembled the loop with no immediate leaks. Those Primochill ghost barbs are easy to put the tubing on, but I recommend wrapping them (to protect the knurling) and then using a pair of pliers to make sure they're in tight enough to seal properly.