My STARCRAFT 14RT that has the built-in cassette potti/Shower combo has a track for the shower curtain which gives you privacy for the potti. It also has a full width pull curtain across the that end of the POPUP trailer which is the one we use the most when the wife uses the potti.
You can see the two ceiling mounted tracks in this GOOGLE IMAGE photo for the two pull curtains (UPPER LEFT HAND TOP)...
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Folding side panel are nice but may be a hassle stowing them when in travel mode. The curtains get opened up and strapped against the window wall that collapses when the roof is lowered down. Storage inside my POPUP is premium space. The only storage area I have inside is the floor space below the cabinet tops. You can't stick a hand in there once we are packed up and on the road... I'm not sure where I would stick some folding panels inside my POPUP trailer when the roof is lowered. Most of the high-side POPUPs like BONDEBOND has comes with the bath room panels...
What model of POPUP are you referring too...
Roy Ken