Ball mounts Is it legal to have one when not towing?

Just a observation about having just a hitch pin on your 5/8 pin. Several years ago a friend of a friend was killed when a stinger came out on the highway and hit her. The most likely reason is someone pulled the pin and the big pin worked it's way out and a bump allowed the stinger to fall out.

I use a grade 8 bolt and nut with a set screw safety. No one is going to get that out unless they have a hex wrench in hand.