I was looking at that book last night, I’ve also read about this until my eyes bled (a little dramatic, but feels like it.)
I don’t want to put tight curves anywhere as I want a nice “flow” and less chance of a loco at model warp speed derailing on a tight curve.
I have seen a few we like the looks of,
i must consist of 2 loops in any shape or size and have a small shunting area