Mustang backrest stays put now!
I ended up using painters tape to protect the chrome and drilled out the stock indentions on the Mustang post. I used a 1/8" drill bit in a drill press. I had to remove the pivoting part of the post (the part with the pad attached) in order to get the indention post to lay flat on the drill press.
I ended up removing the seat by sliding up and over the indention post. Then I reset the detent screw to the correct hole to adjust the height. I put the seat back on by sliding it over the indention post and then reattached the pivoting part of the post with pad (by using the two button head allen bolts with locktite).
Now it works the way I wanted it to! It doesn't move down anymore when I lay on it. As an added benefit it doesn't come out anymore. That should deter theft. This mod isn't for anybody that likes to remove the backrest often or needs to take the seat off frequently. When I need to remove the seat I'll have to remove the pivoting part of the post in order to slide the seat over the indention post. That's a small price to pay to have a comfortable backrest that stays put!








