Ok, I did this a while back, so I'm going off memory.  Per request, here is the write-up

Tools Needed:
2 hinges from Home Depot, Loews, etc..
Phillips head screwdriver
Drill
10 mm socket
Large towel
2 stainless steel washers
Another human (not necessary, but damn helpful)

Install:

1)Buy two hinges like the ones seen in the pics (outlined in red).  Don't go too big because you won't be able to screw down the end, nor too small or it won't be strong enough.


2) Open trunk and lay large towel over rear window.

3) Remove the four 10mm bolts circled in red. After removal, carefully lay trunk on towel (I bet you were wondering what the towel was for, huh..)  You could remove it completely, but you'd have to disconnect the spoiler brake light, so this method gets it out of the way without having to go through that.


4) Take the hinge and place it so that it forms a seven (7) shape on the trunk brace. I show how to in red in the picture below.  Once it is like that, drill pilot holes into the trunk brace so that you can screw in the hinge. Once the holes are drilled, screw in the hinge.


5)Repeat on other trunk brace. Once the hinges are screwed in, take a bigger drill bit and make a hole through the hinge for the 10 mm bolt to go through. Repeat on other trunk brace.

6) You should now have two hinges screwed into the trunk braces with bolt holes through the middle of them. Now you are going to re-install the trunk. Since there are hinges now between the trunk brace and the trunk lid on the top bolt hole, you will need to put the stainless steel washer in the second bolt hole between the brace and the lid. I pointed to these in red in the following picture. This evens it up so you don't have a lid that is higher in the front than in the back when it's closed. Do not fully torque down the four bolts after you are done with this step.


7) After you have re-installed the lid with the washers in the lower two bolts, you can adjust each side so that it sits nice and even when closed.  After adjustment, tighten down the four bolts to hold it in place securely.

8) You now have everything done with the top part of each hinge just hanging on top of the braces. Flip the hinges so the sit flush against the trunk lid and drill pilot holes into the lid for the hinge screws.  After the holes are drilled, screw in the hinges securely to the trunk lid.

9) You are done! Now when you want your trunk to flip down, remove the four 10 mm bolts and carefully swing the trunk lid down.  The latch will come to rest on the lower part of the rear window, so let it down softly.  If your latch doesn't have a rubber sleeve over it (mine did), place something in between the latch and the window for piece of mind.  When you are done with the show, swing the lid back up and replace the four 10 mm bolts, close the trunk and drive away. Here is the end result:




Some people have made systems where the 4 bolts never go back in and the lid is held upright by a bolt-latch, like the kind that hold shed doors closed.  I didn't like this idea because I want the security of knowing that 4 bolts are holding my trunk snug, and not one or two latches.  Plus, it takes a whopping 2 minutes to take them out at the beginning of a show and 2 minutes to put them back in afterwards.

If there are any questions, please ask.