So i decided to try and make a spoiler that attaches to where a wheelie bar is normally since i haven't see one around. This is the result. Everything was pretty precisely measured but I don't have a printer atm to print it out. So if you do decide to print it please let me know if it works.
-Modeled and exported in mm.
-Comes in 3 parts which should slot together.
-significant support material is probably needed.
-sketchup file included as well if you want to mod it.