I recently bought a silver 10x20 heavy-duty tarp, not to cover the Airstream, but to use for a sun shade; sort of a tropical top like the old Land Rovers used to have. We camped in our local campground right after we bought the trailer without trees or shade. We had to park the rear of the trailer to the west, and on a 90 degree, sunny day it just baked. I started a thread about air conditioners not being able to keep up.
Anyway, my plan should I ever need it again, is to set up the tarp end on two extendable tent poles, stake it down and have it go up just over the end cap seam about 1 foot higher than the trailer. The tarp will extend down to the ground behind the rear of the trailer, again not touching it, but sort of as a free-standing lean-to. It ought to shade the end cap sufficiently to allow the a/c to work efficiently. At least is sounds good on paper and the tarp was cheap.
AIR 2053 Current: 2006 Born Free 32 RQ Kodiak Chassis, & 1995 Coachmen B-van
Former Airstreams: 1953 Flying Cloud, 1957 Overlander, 1961 Bambi, 1970 Safari Special, 1978 Argosy Minuet, 1985 325 Moho, 1994 Limited 34' Two-door, 1994 B190 "B-Van"