Center distance spacing on curves is relative to the radius. The tighter the radius the more overhang. Passenger cars and other long rolling stock will overhang at their centers to the inside of the curve. Articulated locos will overhang at the smokebox and cab to the outside of the curve. With that in mind it follows that there will be spacing difference for different track radius dimensions, more for tighter curves than for broader ones.
Crandell's idea is good. Temporarily tack down some flex track to a piece of plywood at the two radius you intend to use and move a couple of cars and engines by hand back and forth on both pieces to check for clearance. Once all is well note the radius of each piece and the center distance and transfer them to the layout.
Lobuc Valley RR
"The Hobo Route"