Can you be smart with your box design and put some kind of slope towards a drainage slot along an inside perimeter? Presumably holding water in this area is the reason they rot. This might be a cheaper and more environmentally friendly option over the plastic coated ply. Do you have a place to park it where it can dry out quickly?
Also i can not stress this enough, get a good cover.
At the moment I'm using an old patio furniture cover, but it's not really a good fit... Any recommendations for cargo trike covers? Tempted to buy an outdoor table cover, slightly oversized, cheaper than motorbike cover from what I've seen.
Can you be smart with your box design and put some kind of slope towards a drainage slot along an inside perimeter? Presumably holding water in this area is the reason they rot. This might be a cheaper and more environmentally friendly option over the plastic coated ply. Do you have a place to park it where it can dry out quickly?