That is really nice. I also have a newly acquired 68 20 footer (Model 208). But my toilet/shower area had been remodeled (Bubba-fied) by a previous owner. I would sure like to see more details on how the solid wall works, if you have a chance. I am trying to source a replacement shower pan, toilet, holding tank combo before addressing replacing the upper partitions.
I have also been curious about the galvanized inset panel visible in your first picture. It is on the lower curb side front corner.
I downloaded an owner's manual from this site but it does not shed light on either of these things.