James Parks wrote:Can the weekender be placed on a 5x8 trailer..I was looking at placing it on the side rails, and use the space under it as storage.
5x8 is the inside dimensions between the side/front rails.

Better get a short step ladder !
You will be 2 1/2 feet off of the ground plus the thickness of your floor.
Kinda like stepping up on your bathroom vanity!
If you are trying for a dual purpose trailer make a slide in but cut out the side rail where the door will be. You can save it and modify it to bolt in if you want your cargo trailer back after sliding out the body.
P.S.
40 cubic feet of cargo storage is overkill unless you are also hauling a cord of fire wood.