I solved the squirrel problem by taking a plastic gallon jug, cutting out the bottom, and placing it at the top of the pole, under the feeder. It has worked for many years. A squirrel occasionally climbs up the pole, ends up with his head inside the jug, and climbs back down. The jug is too slippery to grab onto. The birds are slobs and toss enough seeds onto the ground for the squirrels anyway.
Such a babe!