I decided to modify a rear spoiler with the hope of increasing downforce. I will be making a front spoiler extension & splitter so hopefully this will balance it out a bit. I'm adding fiberglass to a stock rear 3 piece spoiler to make it about 1" - 1 1/4" taller.
So far I've got about 80 bucks in materials and it looks like it'll work. I used some roofing flashing to make a sort of mold on one side of the spoiler to support the fiberglass & resin.
After building up one side with several layers of fiberglass I removed the flashing and added several layers to the other side.
Then sanded with an air tool with rough twist lock 3" pads to create the curves and zip off the excess.
After another coat of fiberglass resin and another rough sanding *I'll smooth out the surface with a skim coat of bondo and prep for paint.