Thanks for the comments so far guys. :-)
Oboe: I definately plan to add additional weathering, including oil leaks and paint chipping. I have a black-and-white photo showing a P-51D from below, and can get some additional oil leak ideas from that. I did use several intensities of "panel lines", with the darkest reserved for control surfaces. I will experiment with the shading idea you suggest.
Fencer51: The "historical corrections to the paint" job I mentioned involves either white recognition stripes (which I hate), or the invasion stripes shown in the old Squadron/Signal booklet from the 70s. I probably will try both, and use whichever looks less strange. I wish I could get away with no recognition stripes, but have no evidence that such would be historical. (BTW, I remember you from AW around 1990. I was "The Deacon" then, and initially was using an Amiga 1000.)