ONAROLL, I do it basically the same as you, but I carpet the bunks prior to going to the ramp wrapping the last piece of carpet around the end of the bunk. Clamp to trailer mounts drill from the bottom side, install stainless carriage bolts from the top and tighten until the head of the carriage bolt is below the surface level. The bunks will never come loose and the carpet will not unravel. Budlight
I just did mine. Any wood will work. I just painted mine with some resin to waterproof them then covered them with carpet.