How about make the hoop house so you can "roll up" the sides a little or a lot, plus have the ends open. That way you will still have a roof but with plenty of ventilation.
My neighbor has a hoop house (or HAD a hoop house) He did not have a sail problem but a snow problem. This past winter heavy snow collapsed it. It's still laying flat in his yard. This was a big one, about 12' wide by 20' long.
