I had my Sonex tied down outside for 5 years (all surfaces polished; the 6061-T6 holds up great outdoors). Wing covers and of course a canopy cover 100% of the time. I never moved them or checked them, or moved the aircraft around based on weather conditions. I never had any blemishes or issues from the covers. The wing covers were quite tight fitting, almost to a fault.
Actually, I did have one "issue" with the canopy cover. Since the Sonex canopy is far from weather tight, the canopy cover should extend back at least 18" from the back of the canopy. A "stock" cover from most vendors doesn't extend nearly that far, and wind driven rain did get blown up under the back edge of the canopy cover at times, allowing water to drip into the baggage area. Fortunately the Sonex fuselage is self-draining (LOL!), but don't leave your headsets or anything that should not get wet, in the baggage area.
Bruce's Custom Covers:
https://aircraftcovers.com/general-avia ... gle-engineWhen some holes got worn in the wing covers Bruce fixed them for free.
I used nylon ratchet straps with open hooks (from Home Depot) for the wing tie downs and never had any issues.The tail wheel was held down with nylon rope and a taught line hitch.
Ailerons did not need anything to hold them in place since the wing covers did that. For the horizontal stab I held the stick back with the seatbelt and a nylon strap (see 27:12 on my video:
https://www.youtube.com/watch?v=Lbgek8-X14o).