If I remember correctly, Sabre is a Forest River product, and the rack is an option available only within their (Forest River) line of trailers, I also believe that the bumper is built to handle the rack, and it's rated at 150 lbs max.
You can check with the guys on Forest River Owners forum, there are a few of them using them.
Ultimately, you could have one custom welded, but I would be sure to have the bumper part of the custom upgrade.
2011 Dodge Ram 2500 Cummins
2012 Starcraft Autumn Ridge 297 BHS