When you say it marks up the top, is that temporary or permanent? I was considering getting these when I put my car in a car show as well, but I'm concerned about damage to the top.
I'd like to add a spoiler to my convertible too but haven't had any luck finding anything up until earlier today. I was on the Steeda site and found a GT500 style spoiler for the S650 and it mentions that it fits convertibles with modification. I'd be interested in finding out what all is...
Same here as stated by Mr. Sub above. My convertible mainly drives the interstate at speeds averaging 75 - 77 MPH and no rattles, vibrations or resonance. It's super smooth and gets great gas mileage on the highway too.