I've got another trick for shimming the trim piece to get the proper gap.
I used clear hockey tape.
I layed layer after layer onto itself kind of like a deck of cards and cut it to the size I needed. About 20 layers was perfect. With the tape I could keep adding layers, or take some away to get the gap thickness right. It cuts easily with a razor blade. The pieces were about 3/4" square.
If a shadow showed up I just trimmed the tape pile smaller.
It worked really good.
I didn't think of taking any pictures, and don't want to tear it apart again, as it looks good and is all back together.