I recently acquired a '72 DSII and am in the process of restoring the (likely original) trailer that it came one. One thing I want to do right away is to replace the currently 2x4 on end bunks with 2x6 or 2x8 boards laid flat.
I came across these solid HDPE boards made by a company called Ultimate Bunk Boards.
https://www.ultimatebunkboards.com/
Generally online reviews and forum posts seem positive. They initially seemed too pricey but, after looking pricing out some decent marine carpet, total cost seems pretty close. Since these have a longer service life, they may actually be cheaper in the long run.
Curious to see if anyone here has had any experience with them.