It's funny that you ask. I just got the idea to build one to feed protein this weekend. I think I'm gonna do a 4' X 4' trough about 4' tall with a tin roof. All I'm gonna do is use 4"X4" corners with a plywood base. Come in a foot (to make the trough) and leave about a six inch gap (for the protein to fill the trough) and the have plywood sides going up 4' to a tin roof extending over the trough to keep the protein dry. I'm sorry if this doesn't help. I have a picture in my head and no real plans. I will be building it soon and I'm an engineer so I should be able to make som designs for you.