you don't need it but it depends on how you like it. I tried a couple trips without mine and decided I like it better with it there. my cooler was just too slippery, even though the footbar isn't exactly grippy the curves are good for purchase. without it a few times through more challenging rapids my foot or feet would either end up under the cooler or wedged in the bailing channel or something. I found I just prefer a more solid surface for when I really want or need to crank on it. it's only a couple inches so it was worth it to me. plus, the lo-pro for my homemade umbrella holder is mounted in the middle of my foot bar.
maybe someday I'll spring for the deluxe footbar.
Teletoes, I did the same thing when I roof racked mine before getting a trailer. I replaced the bolts with a couple spring clips so it made it super easy to flip.
the other thing I found is if you have the room and move the footbar a few inches back from the cooler, is that space in between the footbar and back of the cooler is a perfect place to stash a couple 3 gallon water jugs.