Anyone keeping a fabric plane in the open?

Fabric suffers from UV more than anything. I've seen some
factory-covered airplanes that have almost no UV blocker, and you can
see daylight through the fabric while crawling around in the fuselage
or snooping through acces holes in the wings. It shoud be completely
dark in there; no UV or visible light.
Stits finishes are PVC (polyvinyl chloride), except for their
urethane finishes which are tough and shiny and a whole lot harder to
repair. Both weather well. Other urethane finishes are available but
many don't have the flexibility for fabric; they're intended for solid
surfaces and will eventually start cracking as the fabric flexes.
BTDT. Tires suffer from UV and ozone in the air.
Dark finishes result in more solar heating of the fabric, which
embrittles and weakens it over time. It can, in extreme cases, cause
further shrinkage of the fabric and crushing of airframe structure.
Water from rain, snow or condensation can get into the structure
and cause corrosion. In our climate, the winter snow can be very fine
and dry like dust, and gets into everything during a blizzard. Of
course, such fine stuff has little moisture in it and it can evaporate
(sublimate) when the sun comes out again. And then there's hail and
wind. I've seen some perfectly good airplanes damaged by wind, even
though they're still tied down. Control surfaces and stops beat up,
cables stretched, paint and plexiglass eroded by flying sand. Covers
are great but if the dust gets under them, you now have sandpaper
working on it. Dust gets inside the airplane, too. Adds weight and
clogs things up.
Dogs pee on props left poistioned vertically; saw one that had
holes eaten through it while it had sat through generations of canine
visitors. (Another reason to fly taildraggers!)
Biggest hassle with outdoor storage is probably the birds and
mice and their nests and poop and the resulting corrosion. They can
find ways into almost any airplane. Mothballs keep them out. Might
keep some of your passengers out, too. Everything's a tradeoff.

Dan