Since the upper walls of most moulded fiberglass trailers slope inwards towards the top, the blinds will hang away from the frame at the bottom. I wondered how this was handled, too, and in an earlier discussion another member supplied the same Velcro® answer as Con.
In addition to the hook-and-loop fastener (e.g. Velcro) idea, I noticed that the Escape
has small loops of elastic material trapped under the window frame at each lower corner - when the blind is fully lowered, the loops can be pulled over the ends of the blind's bottom piece, and are held neatly against the frame. This seems a bit fussy to me, but it is easy to do (tried it in the showroom), and my guess is that it would function well.
I still have annoying and ineffective curtains; I'll report on my modification when I choose and install something better.