I have a 70 qt coleman extreme and I fly sparge . . . but not in the cooler
I use a converted keg for my mash/lauter tun, the cooler is a cooler
I don't think you'll want to fly sparge with that thin of a bed, but you could give it a try. But really, why? The easiest way to use that setup is batch sparge, and it works great from what everyone says. Why add the complications of fly sparging? My setup has a sparge arm so it's no big deal, but if I was starting from scratch I sure wouldn't bother making one.