It depends. Some of the frames aren't made to carry any weight on the back bumper. We used to carry our bikes inside our old trailer, but we got a PU last year and now carry them in the bed. Of course it's only 2 of us. Maybe carry two in the front of your tow vehicle, and a 4 place rack for the top?
2013 Jayco Jayfeather X20 E, 2008 GMC Sierra 1500 Crew Cab Z71 SLE