When we bought our trailer (used) it cme with a 2" receiver already on the back.
My guess is that the PO might have towed a boat (hopefully a smallish one!) or something else as there was also wiring to the back for lights.
I initially thought great, I'll use it for a bike rack, but at the same time I bought the trailer I joined this forum and read all the comments about not hanging anything off the back
I was not sure if this applied to all AS trailers or just the older ones but decided not to take a chance and so I cut the receiver off and never did use it.
I'm a retired Mech. Eng. and obviously agree with the additional dynamic loads that UKTOAD mentions with bikes - or anything else - cantilevered off the frame at the back. (Nothing to do with the fact that I am also an expat Brit! - but one who likes big diesel trucks!)
The frames on newer trailers may well be sufficiently beefy to tolerate this, I have no idea, I just decided to err on the side of caution!
Incidentally - I carry bikes on the front of our truck - certainly there are some disadvantages to this, but one advantage is that I can (Just) see the bikes over the hood line and keep an eye on them.
Last week, coming home from Florida on the interstate I saw fifth wheel on a long ramp about to join the road with us. The guy behind him was flashing lights madly to get his attention.
One of two bikes on the back of his fifth wheel had somehow become completely detached at the rear wheel end of the bike and was dragging along the highway! So there is one advantage of carrying the bikes up front!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.