HDDP,

If i remember correctly, the SRT-6 has a governed top speed of 158 mph whereas the limited/base have a drag limited of 151 mph.

Also the fact that the SRT6 can pick up speed much quicker than the regular 3.2 is probably why the fixed wing is there. If you stomp on the gas at 55 mph on an SRT6 you'll hit 100 before the wing is fully deployed making it a possible hazard since it take about 4 seconds or so to deploy. Also the fixed wing creates more downforce due to the larger area it covers (over the rear fenders) whereas the deployable wing is only the width of the rear hatch glass.

But this is all possible speculation since i just think chrysler wants the SRT models to stand out from the regular models and look heavily modded. Look at the SRT8 from 300 and the Charger and then look at the regular car. Alot of the body work is just there for show nothing more. Also the SRT4 i personally don't think needed the wing but if you get the idea of the point im trying to make. I just think they added the fixed wing thinking it would make it stand out more from the regular XFire also look at how they added the extra front lip on the spoiler. Again for stand out purposes nothing more. The car already has what it needs to handle the extra power, reinforced engine piston walls and head, reinforced transmission with 35% faster upshifts, larger front and rear brakes with larger calipers up front, stiffer suspension, etc.