Here is one posted by a member on another board. It is like several already posted in that it uses the channel section and pintle ring. However he has made a modification to connect to the bumper so that it takes some of the load. Pretty intuitive actually. Just wonder what regulating authorities like DHRA would think about it? I suppose if it ruffled feathers, you could leave the bumper attachment unbolted or completely off.
These images don't show it but a bolt goes through that plate and the hole in the bumper for a ball.