Hi June,
At the risk of duplicating/contradicting prior posts from other good folks I would like to offer my thoughts.
I am located in Maine and this will be my first winter with the OTT. I did a fair amount of research, spoke to OTT, and the manufacturers of various covers. I knew before making my purchase that indoor storage would not be a realistic option for me. I also know folks in Maine who prepare for winter by waxing the camper well and remove snow as needed. They report very positive experiences.
With that info as background, I plan to use a CalMark cover as it is specifically designed not to chafe and will protect the surface from potential issues where I park my camper. (pine pitch, bird droppings, etc) You may have read other posts in a separate thread describing positive experiences with the CalMark Cover and the OTT. In my humble opinion, storage for the OTT is like finding a pair of shoes: you must find what fits you.
FYI: After washing, waxing and winterizing I plan to use pool noodles (slit as needed) on the edges of the solar panels. I will also strategically place some pool noodles behind the awning to raise the cover a bit and eliminate the 'valleys' on the roof. I may create a lightweight 'skirt' to avoid build up or drifting snow beneath the unit. This will make it easier for me to 'unwrap' if I decide to bug out before the snow on the ground has disappeared. I used this general approach(noodles, skirt and cover) for many winters with considerable snow on both my boat and a prior camper with fiberglass sides and had very good results .
Congratulations on your purchase of the OTT. I am truly enjoying mine and continue to be impressed with the design and quality of the trailer!
Good luck with however you choose to store your OTT!