I was probably too harsh. The rear roof top wing or spoiler on our car has such a shallow angle that it probably does not produce any significant downforce or add to drag.
In fact, if I recall correctly, on hatchbacks that have deep angled rear windows, a shallow almost horizontal roof extension "spoiler" actually does reduce turbulance and reduces drag coefficient. Extending that a couple more inches at the same shallow angle might actually help high speed handling.
None of this really matters until you get to 80-85 mph. But from then on up, even very subtle changes to a rear wing or spoiler, especially on a hatchback, can make quite a bit of difference in high speed stability. And if the angle is significant, it can rob you of a significant amount of horsepower and adversely affect fuel economy. It would also tend to further unload the front tires, something not desirable in a FWD car.
The suggested mod will more than likely be cosmetic with little or no influence on drag coeffecient, handling or performance.
A digression (hope this is o.k. with mods): I must confess to have taken my MS3 up to pretty close to drag limited top speed. My GPS recorded this as 152 when I looked at it later. I did want to know how stable the car was. This was on stock tires. To tell the truth, it was not as stable at that speed as i would have liked. It was not as stable as a hatchback turbo Saab I owned before, which was rock solid stable when maxxed out at 149-150. I do not recommend this test to others. I've been driving high performance cars for over 40 years and once owned a race-prepped American muscle car in the '70's that with street gearing would approach 170 mph. It was stable, but when I think back on the primitive tires and brakes of that time, it's a miracle I am alive. I was young and stupid then. I don't have the young excuse now. Dunno about the stupid part. I did stick with 4:10 race gearing after that (rather than the 3:23 road gears), which pulled top speed down to more sane speeds not quite hitting red line in fourth gear in the quarter.
BTW: I was alone on that MS3 speed run. There were no other cars in sight during this "performance testing" session. I was just curious about the upper limits. Curiosity is satisfied. No need to repeat this.
I would not want to be monkeying with the rear wing, however, if speeds above 100 mph are ever to be involved. There was also quite a bit of wind noise in the cabin above 110 - the side window seals appear not to be designed as well as they could be. Maybe just my car. The Saab was eeriely silent at extreme speeds, but then it was a much more expensive car.
Sorry for the digressions. Just wanted to say that at normal Interstate driving speeds, the wing extension is probably o.k., and if you like the appearance, go for it.
Think ill get it soon..hope it doesnt fly off lol.
