Just a little more work on the insides.
The larger hole is cut with a 2 3/8" Forstner bit. The smaller hole is cut with a 2 1/8" bit. This will allow the 2" dowel that will serve as the middle of each of the three-disk, wooden crytpex-style lock to go through the center of the PVC sheath. The 2" dowel will eventually lock the thin drawer in place. More on that later.
When you look below you can start to imagine the thin drawer with a center runner. This thin drawer will have a 2 1/8" hole in the center so it will be locked in place until the cryptex lock is open.
Next..the beginning of the locks.