If you can just find something with aluminum frame that is the best. When I used to make them I used a material (butchers use them and UV stable) similar to king starboard for top, and powder coated aluminum. I still have the original prototype one I made with Sculpin (member on here). That one had an aluminum trough in front, and is handy. If you search in US there are dozen companies that make dock type ones. You really get what you pay for with them. My choice still would be a welded aluminum frame any day of the week with the board that you can take off. Makes it multipurpose.
Believe it or not it is more expensive to make it out of 100% plastic. That material is not cheap. Good luck in your search...
This was one of the ones I stopped making while back. I sold quite a few to people with cabins etc.
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