We had the same issue in our 2019 WhiteHawk. I found a soft rubber insulation molding at Lowe’s shaped in a half circle with a flat adhesive back. It was very pliable and easily conformed to the shape of the plywood. I also added staples ever 6 inches or so to help insure it stayed in place. Works great.
We used cheap indoor/outdoor carpet from Home Depot. You can buy it in rolls a little bigger than the size you need. A little spray adhesive to glue it down and wrapped over the edges. Sure helps keep the mattress from sliding and helps keep the sheets tucked.
Used the excess from the roll to make stair pads for the metal fold-up entry stairs!