I have no idea about downforce on an rt. Top on or off complicates matters. Ask the Grail Keeper and pick his brain like I did. Guys on the autobahn say that the nose starts to feel light to them in a GTS. I have not noticed it with driver, co pilot and full tank of gas. However 2 people,full tank of gas, jam the trunk full of stuff and it feels funny even at next to normal speeds on the interstates. Nose sits up higher when loaded. Spring rubbers for the rear springs??I'm going to try color matched canards and the little gt2 splitter not a cow catcher on the front. Should blend nicely with some of the greatest body lines ever seen on a car. Going to skip the fat GF seat belted to the hood just behind the naca duct. Even with her legs spread the additional HP gained like the vipair it was negated by her weight. Next try will be with a skinnier GF and longer legs. I am sure that combo while holding the nose down will provide more air flow and HP than the vipair. Then again long legs might drag on the ground or block airflow to the radiator and cooler. Maybe a midget GF. What do you think. Forget about male viper drivers on the hood. Way too much air restriction to the naca duct. GTS Bruce