I live in an area that gets a lot of rain in the winter time. After adding to the legs on my canopy I did not add any length to the sides, leaving the bottom 2 ft open. I left the front and north sides open also, and I never noticed any moisture problems unusual to my area. The front was facing west (let rain blow in), and the rain almost always comes from the south/southwest here.The canopy top kept anything from dropping down on the trailer, and the breeze/wind seemed to keep any moisture blown away.
Don
Don