Looks like a good start. The bottom of the chin turret is way too pointy, however. What resolution are you working at?
Things to watch with B-17s...
Cheek windows will vary depending on production block and manufacturer. There was a lot of variance on the F model; about the only difference for the G is that early Boeing blocks did not have the large "wedge" windows.
Waist windows will also vary. What you have here are the later fully enclosed versions. Some of the earliest ones had fully open waists and there were also some middle blocks that had windows with prominent frames that divided it into 3 parts.
I'm sure you already know about the "Cheyenne" tail turret.
Late blocks had a shorter nose cone.
I guess what I'm saying is to make sure to thoroughly research whichever plane you're profiling!
Edit: I forgot to mention; if you need photos of any parts, I have a bunch.