I ran a bead of silicon caulk around the opening covered the door with plastic wrap closed it once ( I have magnets that keep it closed) opened it removed the wrap and let it cure, very tight custom gasket.
I don't really have an issue at the door. I do get some sand coming out from the joints. I tried to use some gutter sealer when I put mine together. For the most part, it worked but I still get a little leakage.
l glued everything as l put it together. I have a thick coat of paint inside and out and put a thick coat of white truck bed liner on the inside. Hopefully for me that won't be an issue.
Thanks for the responses and info