Our stock ones functional? I don't think so. Take a look at the way NASCAR spoilers sit, just to get them into the airflow to get downforce. The rules not withstanding. Take a look at the ones on Pro-Stock and Funny Cars. Either they extend beyond the rear decklid, adding more rear area or they stand up above the roof height to get into the airflow over the body. Ones that allow for angle adjustments would work, and there are some mentioned here, but too much angle adds drag to the additional downforce (NASCAR exemplefied), so slower we go, but we have downforce. ;-)