Your bumper will carry the weight if you reinforce where it attaches to the trailers frame.
In this pic, the piece of angle iron that is cut off at an angle, spans underneath the existing frame to the underside if the bumper itself and keeps the bumper from being able to rotate and tear lose.
I carried nearly 100# of bikes over 13 years with this setup and never had any problem after this mod. Before that I ripped this bumper off with just a couple of light bikes.
Note, I'm not responsible for the factory booger weld on the right!