First off, ignore everyone that has been a prick about it. next, look at it from the back.... it is slightly wide, i'd say make it 2 inches narrower from each side, no more. it needs to be dropped down as said before maybe 3-4 inches. also, i would have angled the posts a bit more so the top of the post was a bit more inward compared to the bottom then what it currently is. final piece would be to angle the wing its self a bit more downward in the front.to give it an overall 20-30* angle. other then that i think it looks fairly good. i would not move it forward any, i think it looks solid where the mounting is. the side markers looks pretty good, my only thought with them is they look to symetrical. i personaly think they should be "slightly" more triangular being a bit small twards the front then the rear. but again, my personal thought.
overall it looks nice, good show to design it. take my thoughts with a grain of salt, its YOUR spoiler, do what YOU want.
Torinalth