re: Cargo trailer: removable shelves

get some strong piano hinges or heavy duty gate hinges(whatever your preference mount 2' wide x8' long strips of plywood to the wall at your preferred height...mount eye hooks to top of wall or to ceiling just above the edge of shelf...use chain or heavy duty straps to hold shelf up...

leave shelves mounted and either fold them down (or up...down would be better)flush with wall when not in use and use a hasp in several places to secure it against wall when not in use...

you'll always have them ready and they won't take up more than an inch on either side of the trailer so you can still haul large items...