I always have the roof open. (sometimes I close it for heavy rain). I think the sr cars are at least as stiff, or more so, than the non-sr cars. What does it weigh, maybe 20 lbs in extra hardware? If the heat is on it will compensate for an open roof. I plan to actually get the AC to work better (maybe convert to r-134) this summer, and so the top will prolly stay open then too.