You are both correct. A scale model suitably butchered (small cylinder block, no tailbeam, long drawbar, blind drivers, etc) will negotiate the same radius with or without a center rail.
If you want a more scale appearance, track radius goes up. Center rail simply has nothing to do with that, and deep flanges have very little to do with it. And as MTH is showing, you can keep the big flanges if they make you happy, and still yank the center rail.
