Greetings from the Florida Panhandle
I think that you will find that most long time Airstreamers would recommend against covering an Airstream.
I would never cover cover Lucy unless she was stored indoors in a climate controlled environment. Generally speaking, covers do more damage than good.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)