Thanks fish1sw!
Yes, I made the differential to prevent crushing. You can see how well it worked in the right-side-out and corner detail pictures in the sway.

I did not use darts. I didn't even think of them while prepping/pinning. I'm not sure if it would have made it easier or not. I ended up making up the difference as I pinned the layers together. I just let the outer layer "bunch up" a bit at various points around the perimeter. I'm glad I pinned it before sewing so I didn't get to the end of a side and have excess material.

The pic below is in the sway (about halfway down), but I'll share it here for clarity.
The outer shell is on top in this stack. It is face down (face-to-face with the inner shell). You can see how loose the olive side is. This is after everything is sewn together (on three sides), but still turned inside-out.
WP_20160306_22_33_08_Pro 1.jpg