From the photo above showing my filled can FIFO. To fill the FIFO you simply drop the cans in through the slot on the top of the FIFO. You will notice that the FIFO actually overhangs the end of the shelf it is sitting on by about 2". This turned out to be a blessing as it is easy to remove the cans if you poke them up from below. It is difficult to get a grip on the cans from above to remove them, especially if your hands are really dry. The up-side of having the cans difficult to remove from above is that the cans seem to be well contained and I have never had an issue with any cans popping out without proper poking and prodding. You will also note from the photo that the top of the FIFO provides a sturdy shelf to store more supplies. Just make sure your shelf holding the FIFO is nice and strong to support all the weight. Each can weighs about a pound, so there is about 81 pounds of cans alone, and probably another 20 pounds in plywood.
Overall I am really happy with the can FIFO. The cans drop in and roll down very well. It is actually kind of fun filling it. The rolling and clunking sound it makes when I remove a can is satisfying to my inner child too. For the most part the cans rarely jam, but when they do it is easy to reach in and unjam the offending can. I did notice that symmetrical cans tend to jam less than unsymmetrical cans. In the photo showing two cans, the Del Monte can is unsymmetrical while the Swanson can is symmetrical. The Swanson can has a lip around the top and bottom of the can while the Del Monte can has a lip around the top but the bottom is actually depressed into the can. This tends to make the Del Monte not want to roll straight, which I think attributes to the occasional jam.