I made my own. The secret is removing the rotational moment from the bumper. The Airstream bumper will support the vertical weight but can not resist the rotation a rack produces.
But securing the rack to the window sill this component is removed and the rack works great. The clips are made from old rain gutter hardware and screwed to the sill.
Simple wooden blocks and bolts are used to fit the rack to the bumper.
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