Anything you put back there will not have the smoothness of the Spyder's suspension and will bounce up and down with the back wheel. This motion will actually be amplified because as the wheel moves up and down over a 2" bump, the hitch ball is out on an arm at the opposite end of the hinge point so the ball may move up and down 4". Then your carry attachment is even further back and the rear end of it may move 6" as the Spyder goes over this 2" bump. My numbers are for illustration only and may not actually be accurate but should be relative. A well secured box with just clothing or such may be OK.
I was reminded of this when I pulled my cargo trailer for the first time. It had simple hooks for the chains and within the first 1/2 mile from home on the city streets I had a motorists signal to me I had a trailer problem. I stopped and both chains had jumped out of the Spyder's hitch and were dragging the ground.
I replaced the open hooks with hardware store type carbineers that you can screw tight and even using a wrench they would rattle loose and come off. I finally used some snap-on hooks and they have stayed on.
That ball on the hitch sees every ripple and pothole in the road - amplified. The relatively long tongue of the trailer smooths out most of the hitch movement and makes it more of a slight rocking motion back in the cargo/camper area.
Charles
Has anybody ever caught grief from Law Enforcement, for having the view to their license plate obstructed? :dontknow: