To make my trailer a double stacker, I used four pieces of 2X2 inch steel tubing and a 2X6 inch wood for the top. My trailer has cross supports larger than the for and aft of my boats beam placement. I use U-bolts to attach everything. I take the whole thing apart for storage. I do have to take the back bracket off to remove the bottom boat but it only takes a couple of minutes. I also have two catbox on the trailer for getting everything loaded.

Sorry I cannot find any of the pictures I took of it. It is cheap and it works. If you have the time and money go with John W's trailer. It is at the yard next to mine right now so I have seen it up close a personal...very nice.

Dan