I am in the delmarva area and our winters are a bit more mild than Wisconsin but i did the same thing. I switch from Shrink wrap to a reuseable tarp with a 2x4 super structure to maintain an A-Frame pitch. i have been doing that process since 2021 with success. I have a 22 SLX and bought a 16mil 20'x30' tarp which i tie tightly to the trailer. I have had zero issue with mold, snow/ice, or animals. The tarp has held up beautifully and i have easy access for off season boat work. As of now i have zero plans on returning to shrink wrap.
here is the tarp i bought from amazon for just over 10 bucks
https://www.amazon.com/gp/product/B09BJ2QLLL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
i used about 5 2x4s for the A-frame which i made to be easily taken apart for summer storage. so all in at under $150 dollars and that's lasted 3 seasons so far with no signs of aging yet. Huge savings compared to the near $600 per year for shrink wrap.
The most important aspects i have found so far are a good quality thick material that has UV protection and reinforced tie downs and one that covers all the way down the side rails on the sides front and back to prevent animal intrusion. Good luck with your new cover.