It is the same with the Mustang back rest I purchased a few weeks ago. After installing it, I really wondered how long it was going to take before the seat got cut or worn thru by the adjustment screw(s) on the mounting post. I have the factory seat on my '10 Ultra. The Mustang seats come with an extra layer of leather/vinyl attached to the seat around the slot provided for the back rest mounting post.
Looking for ideas too...

 

Same here and not in picture. did mine last year

 

Hmmm....and I thought it was just me.

 

Me too - no protector in my kit last summer.