If you're interested, our 20" curved bars also measure out to 21.5" However, because of the curve of the bar, the mounting point is not flat. That being said, modifying a bracket by slightly bending the tabs outward, should allow you to easily mount a curved bar in your lower bumper openings.
For what it's worth, our lights fit perfectly on ADD bumpers.
For what it's worth, our lights fit perfectly on ADD bumpers.