A couple thoughts

I love the setting and amount of room you have, but:

1) I'd go ahead and widen the radius in the helix.  Too tight and trains will derail; plus even if it's closer to Livingston, you'll have your back to it. 

2) is there track extending to Missoula not shown?  If not, you appear to have no room to run the power around to the other end of the train for the return. 

Geof

Your Helix

Since you have indicated that you are using modern equipment, I would expect to see bigger engines & longer freight cars than in the transition era.  Because of that, I would recommend building your helix with a larger radius, maybe even an 18".  You could reposition it after or below your module F, Huntley, in that open area and easily get a larger radius. One thing about a helix is that there is an "virtual or hidden" grade factor in a helix due to the friction of wheels on the inner track that actually increases the actual grade so what you think might be a 2.5% grade may in fact be well over a 3% grade.  Another way to compensate for the virtual grade is to make the helix an oval.  

, comments?

  The turnouts on the Livingston module look quite sharp for N scale. I used #7 and #10 on my N scale layout and they didn't take up too much space in that small scale. The turntable looks a bit odd with all the length beyond the turntable , seems like it would be more natural to move it farther from the main and have shorter radial tracks. Since everything has to run over the turntable to get to the tracks beyond I can't see any need for those long tracks. I agree with making the helix radius as large as possible, you'd get a less steep grade with less chance of problems.......DaveB