Thanks for the pics. If I can find a u-joint like that, I might do it that way. But most likely, I will just build me own. After my previous post, I started thinking about it and realized that making my own out of u-tubing and square tubing should be pretty easy.
Now I just have to decide on my plans for the trailer itself. I can't decide if I should have the platform even with the wheel axels or drop the platform down about 6" or so. I think having it even would be easier and probably less material, but drop it down might make it more stable.
I also have to think about how to attach the hitch to the bike.