You can, if your 5th-wheel is designed for a hitch, most are not thought. The ones that can have the hitch mounted already. At leat the ones I've seen. I would say NO, but if you give make and model of your 5th Wheel, we could give you better advise !!
-Point I was getting at is they make a double hitch mounted Scooter carrier's. We have 2-Adly Scooters. The Rockwood isnt designed to mount any thing on the rear bumper, So we have to make room in the truck bed. (note: we have a TT)
David & Annamarie & 2-Pugs (Fatty and Harley)
2011 Rockwood Windjammer 3065
2011 Ford F-250 6.2- V8
2011 Hensley Arrow "NO-SWAY" Hitch