You don't need a spray in liner. The bed is already protected and durable, there is no metal to rust out or paint to chip away. There are seams for the spare compartment (and tailgate extension) that might also make spray-in more difficult, but as mentioned, seems unnecessary (unless you want more "gription") for lack of a better word, so stuff doesn't slide around in the bed as much. Also doesn;t seem worth it, since you have tie-downpoints. A mat of some sort will serve to cover the seams, and make cleaning easier when you are doing messy jobs.
This, it's already a composite bed.
FWIW, my Ridgeline also has a composite bed. It hauls lumber. It hauls drywall. It has had wheelchair ramps placed on it. ATV ramps placed on it. It has hauled lawnmowers. It has hauled construction debris including loose tiles, discarded wood with nails in it. A Christmas tree gets thrown into the bed a week before Christmas and the carcas of one gets thrown into the bed a week after New Year. Hand trucks, hot water heaters, solar panels, gravel, mulch, salt bags, and more.
I don't spray it, I don't line it, it's never been painted and my son even refers to it as "Daddy's Garbage Truck"
The truck is 13 years old and has just under 270,000 miles. Here's how the bed looks after all that hard work:
To me, that's not bad. All surface scratches. To some, it will be. Hope this helps your decision on whether you want to leave it or protect it.
