The
MR Clinchfield layout was quite large - 6' x 13', IIRC. And while it had a long mainline and lapped itself, it wasn't a roundy-round like the one proposed here.
Mark, you're falling into the trap of many new planners - trying to fill up the available space with track. It's a bad plan, both specifically and generally.
The Spaghetti Western style layout inevitably becomes a maintenance headache, and less enjoyable to operate over time, because all you see is track and trains. And, if it gets jammed up against a wall, you wind up not being able to access all that stuff up against the wall easily. It leads to frustration, and no enjoyment of the railroad.
Of course my opinion is based on my tastes in model railroads - I don't like the toy-train setups, I like model railroads. If you're happy with the trainset style layout, then ignore everything I've said.
You've got the opportunity for a fairly good-sized N-scale layout that will give you a good balance between scenery, running and operation. Take a step back, think about what you really want (maybe you do want lots of track and no scenery), worry less about getting lots of track in, and more about how you can fit a decent run in with reasonable curves and siding lengths.