We didn't have any squirrels until we planted oaks on our property, not I have way too many. But we did solve the feeder problem fairly easily: Home Depot sells a squirrel-proof feeder that never fails. Not sure how to add a pic, but i'll try. If it doesn't work, it's a long feeder with a cage, and has metal ivy leaves that cover the holes when the squirrel comes down on the top. The whole frame slides down, covers the holes, and you have one frustrated squirrel. They don't even bother trying any more. Now if I could only get rid of the grackles! They can empty a full feeder in an hour.
OK, this didn't work, so someone will have to tell me how to add a photo!