I wonder how well the hook-and-loop tape will stick to the window surround with temperature swings, humidity and condensation... If you have a clamp ring, perhaps you could remove some of the screws and run them through the tape.
I like that you can remove them completely during the day for
light, ventilation, and views, unlike blackout curtains, which tend to partially block the
windows. My wife likes to sleep past sunrise on vacay, so she would love something like this. We tried blackout curtains, but it made the trailer too dark during the day, so we usually just hang towels behind the curtains on the sunny side. Effective but ghetto.
For heat and sun, it's actually more effective to have them on the outside, white or reflective surface, of course. That would probably require snaps. Hmmm...
If you decide to try them, please post a review.