(sniff) I feel left out!! I run 16" "traditional" passenger cars, on O72 and O60 radius Fastrack . T he O48 necessary to make the layout is under a tunnel.
As I have said in other threads- model LAYOUTS in O are all caricatures, anyway. I found that the minimum actual turn radius for prototype railroads is 410 feet, or 820 feet in diameter. From that I calculated that the minimum actual SCALE turn diameter should therefore be 17 feet, or O-205. Looking at the basement, and checking the Fastrack available- no go.
My visitors, including some train hobbyists, never question IF my trains, the track or the layout is actually a scale model. It's a hobby. If 16" trains, three- very tall rails, "traditional" sized cars that are too far above the non-scale rails, with huge wheels, and lobster-claw couplers makes the hobbyist happy, it's all good. The fun parts for me are learning about trains, running trains, painting, and weathering, building kits...and believe it or not- maintenance.