Shifty, I attempted one of these schemes last year. I'll do my best to explain the problems.
The reason that the "Comet" schemes aren't done has to do with how the cowl bulges are done with the skin map. There is a seam that runs horizontally through the middle of the bulge, then at the cowl hatch panel line, runs at an upward angle to the base of the windscreen. You can see the seam here on this G-2, look for the difference.

The G-6 uses the EXACT bitmap as the G-2, only the areas that are bulged get stretched to fit over the larger area. On the G-6 that seam has other angles on the bulge. So, not does that area look pixilated because of the stretching, but the oddly angled seams mean that lining up the sections of the comet so that they display on the plane in game correctly is near impossible.