As you know, I've been thinking of doing the same scheme on mine, but I hadn't realized the point about the missing white on the upper wing roundels. Unfortunately my job doesn't involve any tools more high-tech than a pencil. Might push me into a different scheme with standard decal-sheet roundels.
One thing about the roundels: I've been looking hard at all of the pictures I can find, and it's surprising how often the upper roundels (and sometimes just one of them) appear not to have white. I wonder if this might be an artifact of the lighting and of ancient photographs with poor contrast.