There's a lot of different theories here. My guess on the speed demon placement is due to the bulging rear end for tires and having an available high pressure area ahead of the rear tires to take the air from efficiently. Relativism from many other cars both land speed and others says top of the car works best. If you look at LeMans and Daytona prototypes which have rules that encourage efficient downforce they intake air from the top at the front and exhaust at the back at the bottom. I intend to take air from a high pressure spot on top, but will wind up testing at least 2 styles. The most conservative, surefire solution seems to be a scoop like the Burkdoll and Burklands cars.