I haven't built a layout yet, but I did some testing to see how tight my curves could get. I used duct tape to hold some track down at a 12" radius. As you see the corners of the loco and cars are very close, but they aren't touching. Oops gotta re-glue that break wheel again. And I have to make some hand rails for my caboose. But really the whole point was to see how small a curve I could do with my rolling stock. If one were to do 55n3 a layout it could be as small as an N scale layout. I am likely going to go with 15 inch curves, but it shows me I can have spurs be as tight as 12" which allows for a great deal of design freedom. I expect I will be making something with a 3x4 footprint and just a pair of switches. Now to find the time to actually lay some track down.