I don't think many single axle trailers would unless you seriously over or underloaded the weight imposed on the towing hitch, we used single axled car trailers back in my banger racing days, putting something weighty on would sometimes lift the back of the towcar clean off the ground, didn't seem to do any lasting harm...mind you even a Zodiac had some serious main integral chassis members.

Twin axled though are a bit different, i've felt horse trailers knocking my previous Landcruiser about, and my horse trailer was Dutch built with really soft coil sprung suspension (giving a very smooth ride for the nags), could easily imagine permanent damage to a tow vehicle less well made, especially if the ride height was wrong to begin with...Dixon Bate make some very good height adjustable drop plates with rubber shock absorbers built in, mainly to protect the trailer from substantial 4x4's but no doubt help the other way too.

I wonder if the Berlie is designed to bend slightly as its loaded, not being funny here, some modern lorry trailers assume a convex upbend shape when empty and level out when loaded....you'd be shocked just how far the front end of a trailer chassis bends down from the weight the ram imposes with the initial tip of a fully loaded tank...the Berlie is a commercial vehicle so maybe some flex is designed in.

Edited by gordonbennet on 05/05/2015 at 20:25