Not sure I'd really call it a 'Mod' but might help some folks.
Went to Walley World and bought the super size auto shade and the back seat 'kid' size with suction cups.
The super size (made with wire so they flip open and store compact), fit the rear window perfectly of our creekside 20fq. Yup that huge back window that so much heat can come in is much cooler when the sun comes around. I'm thinking flip it (black side) if needed in winter. Haha. Anyway it sits on top of the window sill ledge as shown. A bonus for airflow if you're lucky enough to not run a/c.
*** If boondocking this is incredibly beneficial to keep the unit cooler without needing the Jenny's while waiting for cooler evening air.
The other pic, is the skylight in the bath. I bought a thin foam backed sun visor (same idea - auto shade) at the dollar store, Cut a piece to fit slightly larger than the suction cup visor (cut to window size) then cut a slit at each end to let the suction cups thru.
Man! I was amazed at the difference in temp in the tub!! Also, by using a light foam reflecting shade, it allows some light still in. Left over foam shade material? I cut a square to fit the top of the fleece inserts in bath / bedroom.
Not pictured - regular size wire auto screens, fit all other windows perfectly and easy to pop in and pop out as well as store. (Minus kitchen window).
Just be sure to place shades on other side (closer to window than you) leaving the strings tangle free from the waffle pull down blinds.
Hope this helps others stay cool (er)