Now I'm Gettin' Too Big For My Britches

[Cannonball]

I don't think 4% will be that much of a worry on a layout of this size. There would almost have to be a tail-chasing train for that to be a concern-- or a really puny locomotive...

On the rerailer question, I use them generously in staging areas and anywhere there is hidden track. They've saved me from major pileups several times.

Good to know on both points.
I plan to have at least 3 of the rerailers at various points on the layout and was planning on putting one in the far back tunnel. I figure that might be a good thing since the layout will be sitting against a wall and getting to the back portals might not be the easiest thing to do.