FWIW, I'd move the switching activity to inside the center of the layout...at a 20-45 degree angle....and then use 0-54 or 0-60 curves on the outer main....or something to that effect.
I'd also try to bend your "straightaways" a bit so that the loop running isn't as obvious.
No offense....and I only say this b/c you're in the planning stage right now and can alter anything....but this layout will get boring....pretty fast.
It could be OK for your first layout just so you can learn things as you go.....but I'd strive for something a bit more interesting.
Also, can you increase the length to 12-16 feet?
Just trying to help...not be critical.
