I'm planning on cutting my painted front bumper to match the GT version with the cut out for the oil cooler. Can anyone who has a GT bumper tell me the correct size of the cut out, including the size of the corner radii? Is it enough just to make the cut or do the edges need to be rolled back,
if that's even possible?

Yes, I would like to know this also. I have been considering doing the same with my front bumper. I plan on cutting the metal front bumper and my special edition front spoiler to mount a front oil cooler. Don't know if I will put the cooler in the front trunk or just mount it in front of the front bulk head.
Measurements are more important than the radii. I will just make it look neat and matching.
Just the basic height and width will be sufficient for my needs.
thanks

Bumper
19 3/4"
1 3/4"
1/2" Radius

Valance
19 3/4"
1 3/4"
1/2" Radius

I decided not to cut the bumper; the GT valance give me enough air flow with the stock bumper:

Thanks Eric.