Thanks!
All cables are now sleeved! Good job too as I'm down to about 5m of paracord left from the 60m I bought.
Here's where I'm at now:
At the last minute, I changed where the 24pin was going to be routed. I had already cut a hole into the motherboard tray for the cable to go through but, as I discovered with the 8pin, it would have crossed the tubing. And I didn't want that. In the end I routed it up and over the radiators, and then out of the case inside the gap between the inside and outside of the case (where the SSDs are). Routing it here will mean that I can't sew it, but it'll mostly be hidden anyway.
(It'll look better than that when it's finished.)
I also changed the PCI cables so they fold back on themselves, instead of angling towards the PSU. I'll need to cut a hole for the cables in the rad mount so I can hide that mess in the unused space behind the original front panel.
I also found a better way to manage the cables behind the radiators. By moving the fan PCB to between the bottom 2 radiators, the 8pin and SATA power cables can fit around the edges better.
The Molex cable will mostly be hidden underneath the radiators.
The end is now in sight!
I still need to cut a hole below the motherboard for the tubing, as well as in the optical drive bay below the PSU. Hopefully everything will line up for me and I can just crack on with the tubing.
Speaking of tubing: acrylic is a lot harder to work with than normal tubing. A lot harder.
