A funny thing happened on the way to the decal plotter...
I used a steel rule to measure the lamps. I figured, if I get one end of it, the other end will be the same. Perfect rectangle. Got the dimensions plugged in and cut a practice decal. Fit great on that end. But then was a tad too tall on the other end. WTF? Checked the cut and it was perfectly done. Checked the measurements on both ends and there's a super slight TAPER along the length of the reverse lamp edges. Not noticeable since it's only 1/8" along the nearly 19-11/16" of edging.
The inside end of the driver side (the one I used as a model) is 2-1/16" tall, and the outside end is 1-15/16" . The inside edging in front of the license plate lamp area is 5/32" wide, with the rest of the edge being 3/16". Now the difference could be from the mold, or something else. Either way, it would take a bit of massaging to the mylar dimensions to get it right, but would it be just for this particular piece?
Can it be done? Maybe. Are all the measurement "flaws" the same, or will it make a difference as to which mold was used? They used several different molds to make these parts. It wasn't one at a time, I can assure you. Was it on the factory pieces too, or did it just affect the replacement GM parts? I don't know. I'll have to measure the ones on the car to check.
Depending on the outcome, I'm not sure it'll work, since the mylar is not very flexible.