Gordon, I totally agree about the white making things "pop". I had all the same "jewelry" aka badges on the old car when it was silver. Boy, did that change when the car was repainted white. Everything stood out, even the snaps for the tonneau. But especially the emblems and badges. It will be the same with the PCCA sticker. Whit background will make it stand out, do clear if you want to be subtle.
I put my little PCA sticker on the right lower corner of the windshield. The left is taken up by registration and yearly inspection stickers in NY. And as we know, real estate is pretty limited on the glass.