that's a really nice looking piece(as is the GT500 nose)! though i bet you could get a few more buyers if you produced a version to work with the factory hinges. you gotta remember that the atmosphere we live in is pressurized(14.7PSI at sea level), so everything within the atmosphere is experiencing pressure from all sides. so, as a car moves through the air, it's forcing the air out of the way above it, below it, and around the sides. the air that is flowing around the car wants to fill in the pocket of space that the car is taking up(since the air is pressurized), and as such the air is pressing on the nose of the car, on the sides, up from the bottom(creating lift), and down from the top(creating downforce). so, as the air flows over the roof and down the rear window, it's pushing down on the car. adding a prostock style rear wing extends the rear of the car and extends the time that air is pushing down on the car, trying to fill in the pocket that it's taking up. now, there is space beneath the wing that the air can press up on as well, but remember that the car is moving so there is a low pressure area(vacuum) beneath the wing that the high pressure area above it is trying to fill in. so, the faster the car is moving, the lower the pressure is beneath the wing and thus the more downforce it produces. this is the same way a conventional wing(airfoil) works, the shape of the airfoil(when used to produce downforce instead of life) creates a high pressure area above it and a low pressure area below it, and downforce is created as the high pressure area presses down on the wing in an attempt to fill in the low pressure area below. so, yes, you would be wrong, a prostock style wing does create downforce.