I have a '13 F150 Ecoboost, GVWR 7100#, RGAWR 3850#, payload 1607#.
After searching for 53 weeks to find a nice used one near home, I bought a FunFinder Xtra XT-245. 



Max axle weight: 7000# (2 x 3500#)
GVWR: 7765#
Brochure weight: 4650#
Yellow sticker "as built" weight: 5025#
Actual weight with two dirt bikes (~550# total bike wt.):6740#
Axle weight with two dirt bikes: 6000#
Towing this trailer loaded for camping with two dirt bikes, with two people in the truck, the truck is only 180# under GVWR and only 50# under RGAWR.
I liked the FunFinder XT-276 that I have seen touted as "1/2 ton towable", but it would have significantly overloaded my truck.
A fifth wheel toy hauler just doesn't work with a 1600# payload.