I bought a round top Shelter Logic 12' W x 12' H x 28' L building. I put it behind my existing shed, they're the same aprox. length, sheltered by the shed from the wind and by trees, to keep the sun off the cover. I threw down stone for the 'floor' surface area, and built connected 4 x 4" PT as a base for the feet to be lagged into. I drove rebar through the 4 x 4's to keep them from moving and secured everything with the cables and ratchet straps. I also used plastic coated aircraft cable at both ends at the very bottom of the outermost tubing sections to keep the 'mouth' from being able to open beyond specs.
I've had this SL in place here in VT with ridiculous amounts of snow, wind, ice, rain etc, and never once given a thought to clearing the snow or ice from the top or sides.
I use zipper lube from West Marine to lube the zippers to make them function. They are, IMHO the weakest part of the entire setup. This last winter the zippered door on one end did break the zippers. I bought a kit that allows for zipper replacement, IN PLACE, but have not installed them yet.
I would not buy anything but a round top unit in any northern clime that experiences large amounts of snow. I've had this unit up for at least 6 years, no problems other than noted.
Take time, do it once, level, square, plumb, and as protected from exposure to high winds and sun, if at all possible.