If it will help at all, I've studied Erich's Avatar picture closely, and applied some of my (slightly rusty) photo-interpretation skills from both my military and photographic trade days. Allowing for the fact that I'm looking at an 'electronic' image of a B&W reproduction, the tonal values suggest that the area in question is painted. In support of this, I would offer that, just visible in Erich's picture, are what appear to be lighter streaks, presumably caused by the hot exhaust gases, which correspond approximatelty to the positions of the individual exhaust pipes, or at least to some of them. This 'streaking' is also visible, albeit very feintly, in the picture of '7' from the starboard rear quarter. In comparing these tonal values with the paintwork of the camouflage colours, I would hazard a guess that the streaking is a greyish, or greyish brown colour, whilst the 'painted' area is a very dark colour, probably very dark grey, almost black. This would fall into line with certain types of heat resisting protective coatings, designed not so much as a 'cover' for staining, but to protect the metal beneath from heat and the corrosive effects of the exhaust gas. If you look at the known dark areas, such as the prop blades, which I am assuming were schwarzgrun, you will see the difference. the latter colour, although very close to black in normal viewing, registers as a slightly lighter tone on photographic film which, again, can be seen when looking at the spiral on the spinner. If I had to make the choice, I would say that the semi - recessed panel behind the exhaust outlet in the cowling, as shown in Waynes picture, is painted in a very dark grey coloured surface coating. Of course, I could be wrong, but I don't think I am!
And yes, those boys really do look so young!
Terry.