I'll echo what Mike stated above. I love the big B-17 kit but you're not going to see much of it once it's all buttoned up. I think what's up in the nose section will be the only thing you can really see but that's about it. In the cockpit, all you're really going to be able to see is the top of the pilot/co-pilot seats.
When it comes to the waist guns, I attached the glass and painted the frames. With the frames painted and the gun in place, again, you're really not going to see ANYTHING on the inside at all.
As for the tail gunner's station, you're going to see even less. If you're going to focus on anything regarding the interior, I think I'd stick with doing a bang-up job on the nose section and that would be about it. As always, it's a matter of personal preference.
For me, if I can't see it, then I'm not dealing with it. On my last B-17 (about two years ago), I tried to do my best work on the nose area. I do have Monogram's "visible" B-17 in my stash. Since you'll be able to see the entire interior on that one, I'll go all out with the aftermarket and scratch-building on that when the time comes to build it.
Hope that helps!
Eric
PS. Now that I think about it, once I finished my last B-17 I hung it up on my youngest daughter's bedroom wall. Ever since the day I hung it up, I've never looked in the model's interior at all.