The rear fascia on the Na Solstice and the GXP are slightly different but the removal process is the same.  the following is a set of instructions that appeared on the Solstice Forum by PURE Fun

 

http://www.solsticeforum.com/forum/f62/removed-fascia-cutout-honeycomb-back-14342/

 

Removed Fascia and Cutout Honeycomb Back


Before starting you will need to get new plastic fasteners from the dealer!

I started work on Sunday afternoon to remove the rear fascia and paint the honeycomb grill part, but I decided to cut out the back parts of the honeycomb. There were about 200 to cut out, but first to take off the rear fascia, and cut to the point here are the problems, 2 metal clips on each side of the fascia. First snap off the 5 plastic press-in fasteners, the fascia will be loose at the bottom. I jacked the car up and got under and put a snakelite aimed at the 2 clips.


http://www.knkdesign.com/solstice/f/clips-66.jpg

This shows exactly where the clips are located. Insert a screwdriver in the clip to raise the prong up out of the hole in the fascia then flick your screwdriver up to get the clip off, do this both sides. Another way but harder would be to remove the wheels and then remove the plastic wheel wells and you can reach in through the wheel well. After clips are off push down the 3 tabs where the clips are and it will drop down from the rear cover.
http://www.knkdesign.com/solstice/f/clip-locator-63.jpg

Next take a putty knife and slip it in at 8 places you will see each place where the tabs are when you pull out the fascia towards you. You need to push the PK in and down and pull the fascia each time, this will go fast and then the whole fascia is off.
http://www.knkdesign.com/solstice/f/putty-52.jpg

Here is the fascia removed showing all the location points for the previous info removal:
http://www.knkdesign.com/solstice/f/fascia-55.jpg

Here is info about the rear of the bumper. There is no way a center exhaust is going to exit in the center of the grill because of the bumper.
http://www.knkdesign.com/solstice/f/fascia-off-56.jpg

http://www.knkdesign.com/solstice/f/info-58.jpg

Here is the grill all cut out. But to do that I originally thought I would use a Dremmel  but after try to cut just one hole I knew it would not work. The plastic is almost like rubber and just balls up, no clean edge. So I used an x-acto knife which worked very well, I scribed a line each side about 3 times each and the hole would come out. I cutout about 80 holes before stopping. I took the fascia inside and started to cut with a new blade and it just would not cut like before when I was in the sun. Next day I took it back in the sun, which heats it up and it was cutting as usual. All total it took 4 hours to cut cut and clean up.
http://www.knkdesign.com/solstice/f/grill-cutout.jpg

I masked, primed and painted chrome which does look good. But I am going to take a sander and sand down the back about 1/32" there are just some areas that are not right. I would suggest instead of cutting use a sander.
http://www.knkdesign.com/solstice/f/grill.jpg

http://www.knkdesign.com/solstice/f/done.jpg

http://www.solsticeforum.com/forum/attachments/f11/3523d1135859935-painted-rear-grill-solstice_aggressive_rear_valance.jpg

 Here is a picture of the rear Valance painted Body color posted by LatinVenom on the Solstice Forum.