Yes, you remove the rear valance when you put the defused on.

Spray it with SEM "Bumper Coat"

It's tough stuff, and it comes in a can (so you can re-apply without removing the piece, or paying a lining company to re-apply)

keep in mind, if you drive the **** out of your car (like I hope you plan on doing) this part will take a beating, and need to be touched up from time to time.

 

actually it's a really good idea. Dcrosby's FD has rhyno lining on his diffuser. I got a chance to see it once and it looks great. The lining really makes into a solid piece and the end result looks factory.

 

You'd be surprised what people have ryno-lined these days...that stuff works.

 

Here's how I did mine.

I lightly sanded it down and used a quality primer as light coat coat on the FRP. I then used a specialty textured black plastic paint from Rust-Oleum to finish it. I give it 7 light coats (following the directions on the can). I tell you this stuff is tough! I have not worries of it flaking off or chipping from flex or "minor" contact.

I also added additional mounting holes to pull it tighter to the body. The pics below were not the final fitting. I had loosened all of the mounting screws and was able to get the fit much better (near perfect).









I also drilled 1/4" holes in each of the fins (towards the front of the car, this the lowest part of the defuser) to help drain the water out of the defuser. You can kind of see them here in this picture (they look sort of white).


It's been on the car for over a year now with no flaking or chipping.

 

I didn't move it, but since you asked:

It is FD related, but more specifically it's Exterior related.

SilverBullet, that install looks awesome...... I'll use a few of your tips when I install mine

 

I left mine unpainted as well.