Back when I had my accident my throat was bruised from the seat belt. My mom sewed a contraption together that brought the over the shoulder strap down and over a bit so it would not do that again.
To my knowledge there was nothing like it on the market at the time. She probably should have gotten a patient on it.
I’ve been using that “M” design for more than 15 years. Can’t remember exactly when I bought it, but it was at an Auto Zone or Advance Auto Parts store.
Back in the 90s when I rode in a Telco cube truck (I made the young guys drive) I used to tape the cross chest belt to the part of the belt that ran up from thew floor through a “D” ring on the door frame. It never retracted properly, but it stopped cutting my neck.