Mounting bikes at the rear of
any trailer, even though many do it anyway, is a poor idea not just because of the potential for having the mount fail and the bikes scatter all over the highway but also because doing so unloads the trailer tongue. Sure, it may not be much weight overall but at the far rear end of the trailer the leverage will be greatest and will have a negative effect on tongue weight. A far better solution is a bike rack designed for the purpose that mounts over the trailer's A-frame, such as these premium quality
Arvika Bike Rack Systems which if anything will
improve the gross tongue weight to gross trailer weight ratio. :B