Thank you, Greebo. If you look closely at the skin where the fuselage meets the base of the tail - that shading is produced by the Ambient Occlusion technique you described in your P-38 build log. So that's all you. I've used that technique on the engine cowl-wing and horizontal stabilizer-fuselage joins also but it is most apparent along the base of the tail. This is also an area of stretching so it took a lot of trial and error adjustments to get it to look right.
One thing, while this skin looks fair in bright sunshine - inside the hangar, it's a different story altogether. It looks terrible. Its just a bluish-gray pulpy mess under hangar lighting conditions. I wouldn't expect someone looking at B-17Gs in the hangar to choose this one based on what they see there. The bare metal P-38s I've done look OK inside the hangar, and compare well to other P-38s in hangar lighting - but not so for this behemoth.
I am sure I'll be doing at least a few other natural metal B-17Gs. I have a few in mind, and continue to browse for more subjects. I'd be interested to learn about any dedicated bombing squadrons who would like a B-17G skin done.
There are quite a few B-17 skins up for adoption, but I'm ambivalent about whether to adopt and redo them. There may be players who like them just as they are. I'm open to encouragement on that matter.
Here's one from the 100th BG that caught my I recently as a potential skinning subject: