I wasn't happy with the height of the dividers, so this morning I disassembled the setup and cut the dividers' height down from 110 mm to 95 mm. While I had the dividers out, I shot a few more photos. The first photo shows the divider system upside down so you can see the cutouts I used to clear the reinforcing ribs on the bottom of the Systainer. The second one shows the different end cuts needed on the side-to-side dividers. The shorter ones fit in the rear half of the Systainer. The third photo shows the cut pattern for tops and bottoms as well as the rounding needed on the front-to-back dividers required when slipping the assembled dividers into the Systainer. The fourth photo shows the modified dividers inside the Systainer. The final photo shows the way the abrasives fit inside the dividers, and how much easier it is to reach the abrasives now. Sorry, Brice, I don't have any skills with Sketchup. Copy away, guys.
Edit: One thing I would do differently next time would be to cut the slots in the front-to-back partitions from the top to the bottom, and those in the side-to-side partitions from the top down. That will make assembly a bunch of easier.