Even after poring over your photos I don't understand what I am looking at. Could you please describe it? It looks like a curtain rod holder AND the shade hardware are BOTH screwed into the window frame.
I, too, wanted shades to block out light
so I improvised (with the suggestion of a fellow FiberglassRV reader). I simply cut a length of Ron-Loc, a blackout liner fabric available at most fabric stores, the width of the inner span of the already installed curtain rod holders and longer than the height of the window. The bottom edge hangs down below the bottom window edge.
I sewed a channel on the top to hold a dowel cut wider that the span of the curtain rod holders. I sewed a channel on the bottom to give strength (you might want to put a flat board here as is the case with most commercial window shades). On the back of the bottom edge I sewed the hook side of Velcro so it could "stick" to the rat fur, providing a better seal to block out light
With the "shade" in the open position I put it behind the curtain rod and feed it above the curtain rod holders. The dowel rests on top of the curtain rod holders. I roll up the shade by hand and it stays in place. At night or when under tow I roll down the shade, anchor it with the Velcro and we are good to go! This system has worked well for us and does not require any drilling!
The photos show my initial set-up whereas I put Velcro on the top and bottom. When I did that I had to take down the fabric, fold and store. Later I improved the system according to my description above. Sorry, close-ups are not likely soon as the trailer is housed one hour from my home.