For the bumper, I just split double sided tape up the middle and put it on one side of the double sided tape that comes on the chrome trim. This makes it closer to the angle of the original profile. It's not perfect but it works.
After looking at the photo, it looks like an extra full size layer of double sided tape on top of the split piece would bring the thickness closer to original. I'll have to test this on a spare bumper.
Here's a shot of an original bumper piece (I just did this swap on my black Mark VIII front bumper). Notice the angle of the surface with the adhesive still on. It was hard to get a good shot of it, but you'll see it when you remove yours.