I sent naked pictures of my cat to Keith so he shipped my brackets first.
Here's the new look sported by the cool kids this season:
The metal in the gutters is very thick and I'm confident tapping the 5 holes per side for M6 1.0 and running the button heads in with some thread lock would be plenty to keep things attached. I overdrilled for M6 on the 4 points I did mount before I thought of that better idea so I've got nylocks back there. Not sure what I'll do with the other 6 holes for these are fine for sitting in the garage while I think on it...
A few install tips:
1. Mount the wing in place, get everything drilled and/or tapped with the trunk lid all the way open or off. Once you have that done, remove the mounts, lower the trunk and reassemble. You don't get a bunch of room to get drills and arms inside the trunk in the 'closed' side of the mounts.
2. The mounts are sharp. If you are putting these on a street car, sand the sharp edges off the bottom of the mounts so they don't cut the paint in the gutters. You might also want to put some tape down around the area so you don't scratch anything pretty.
3. My clearances are TIGHT. I'm making pretty good contact with the trunk lid so you might need to work some angles to not scratch things on a dual purpose car.
4. Rivnuts were discussed earlier in the thread. The 1/16th of an inch per side that they would push the mounts inboard would make my moderate interference unworkable. Drilling and tapping or traditional nuts are necessary on mine.
5. I don't know how far back these were designed to be but I matched up the back of the mount with the spot the gutter falls away. The angles seem to match up well so my hunch is I got it right. I put some blue tape to keep the metal shaving from falling down behind the tail light.