How easy is the install in a GTS?
"Nothing's hard, but nothing's easy" Ever hear that one? Just kidding though, its not "hard" so much, just tedious.
Here is a suggestion to make the install go faster-
1. After you take the seats out, do your layout for the belt slots right on the center and side bulkhead trim pieces. This is an easier way to work on them, because they are securely screwed to the car, and won't move around on you.
2. It may be possible to do the cutting while the trim pieces are still in the car. This has the advantage of reducing the possibility of mis-alignment of the outboard slots, where they bridge between the center and side trim pieces. Since they are already in their factory offset position, you can cut the slots as they sit, and the finished product will look very neat. It also gives you a lot of support for the cutting process. After you cut the slots, you can just remove the trim pieces, and proceed with the instructions.
When I did mine, I wasn't sure what the factory vertical offset was between the center and side pieces, so I guessed at it a little, and got it off a tad. While I later trimmed it up better, I still wished that I had started the layout with the pieces as the factory had installed them in the car, cause it would have been faster, and netted a neater end result.
Also, Don't do like I did, and think the slots need to be the 5/16ths minimum. No one is going to look back there, and if you make them 1/2" wide, it won't hurt none, and they will be easier to adjust.
This may also help prevent the straps from chaffing on the slots. Chaffing can reduce the rated tensile strength of the webbing. For safety, I would rather err on the side of caution, make the slots wider, and not even risk chaffing the webbing. (But only a guy who hit the windshield after his shoulder belt snapped probably would worry about that.)