Trivial Psychic; prop wash was an issue in that I tried to avoid it as much as possible, but I gave myself a little bit of allowance in the "this isn't real" department. Originally the engines were right in front of each other. I'm really hesitant to redo the wings though, just because they took me
forever.

And yea, it is a radar dome.

Moving the engines out to the wingtips would increase structural loads dramatically, and any sort of maneuvering would create inordinate amounts of stress on the wings - you're putting a ton of weight at the very weakest point in the structure (the end).
You'll get a not-insignificant structural benefit from the combined tip (creating a box-frame without support in the middle), but I don't think it'd be enough to offset that weight.
Thaeris probably has the best solution, with an inter-wing push/pull pod. I tried a push/pull arrangement before by mounting it in the wing (basically what I have now except each of those nacelles had a propeller in the front too). I didn't like how it looked, but I might try it again. Right now I'm working a bit with the interior, to give me a better and more logical placement of stuff in the exterior.
As for aerodynamics, Thaeris, I am trying to keep it as realistic as possible (especially when it comes to the airships, I really want to avoid the "magical floating metal hulk with tiny gasbags" syndrome).
You're welcome to post it on the X-Plane forum (link me!

), but I'm giving myself a bit of a berth when it comes to realism.

Debate on the designs is always useful because I'm sure I missed some stuff.

I would be interested to see debate on this design, as I've never done wings like this before.
So yea, when the school year starts to die down again, I'm going to be going at some of the detailing - windows, any weaponry, hangar objects, etc.
I should post the design system I came up with a few weeks ago, it let's you get a reasonable approximation of the airplane just by sketching.