8" Min. No switches on slopes. A single reverse loop, probably convert it to an industry spur to a city in that area, or passenger station.
A single reverse loop of course needs a 2nd.... I could make the blue line a reverse loop and have a single main on that peninsula. I am not sure I want to do that.
The spur leading to the purple spot is a leftover from a previous idea, I just haven't removed it yet.