I have pulled a trailer for about 14 years now and with 3 different bikes. I would tell anyone going to purchase a hitch for a bike to get a "swivel hitch" or a "narrow shank ball".
I have used the narrow shanked ball and on each bike and (with the help of a friend) lay the bike over to make darn sure I can corner and not have the trailer hold me up! If it ever did I would replace my narrow shanked ball with a swivel hitch before I ever pulled the trailer.
That narrow shaft or swivel hitch will save your life.