If you are realy interested in mounting to the curved end you will have to take the end cap down and apply a reinforcement behind the area you want to mount to. I would suggest fiberglassing an area at least 2 ft by 2ft using several layers of 6 oz. glass cloth.
I have used this technique, to a much small degree to repair cracks at the ends of the cabinets in the end caps.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles