I have a small layout with a 15" 16 1/2" and an 18" radis curves. I have run everthing (with cars) but the Forney. I even ran the 2-8-0-no problens and my track is Atlas 100 code track. just a note the 2-8-0 also runs at any speed. But yes, 18" os more forgiving. I did have to shim up at the beginning of the 15" curve.
' is much more forgiving.
' is much more forgiving.