The Ford "puck system" uses pins to lock the hitch to the underbed receiver. There is about 1/2" of extra space between the bed and the bottom of the hitch legs, so I can't see why a piece of rubber matting or a bed liner would cause any problems. It's still "metal on metal" whether the space is empty or has a liner taking up the space.
I do remember a caution in the CURT installation manual with regard to installing "in bed rails" on top of a liner. The instructions called for either removing the liner or cutting away the section directly under the rails so that compression of the liner wouldn't allow for loosening of the bolts holding the rails to the underbed structure.
Here's the caution that's in the CURT installation instructions:
"3. Do not install mounting rails over plastic bed liners. Plastic bed liners must be cut out of the way. Mounting rails may be installed on spray in liner. Note: Consult installer for recommended curing time."
https://www.curtmfg.com/masterlibrar..._16100_INS.PDF
Now, as for "police ticketing violations" ???? I don't know of any place where any law enforcement has ever checked my setup for that kind of "violation" ?????