We were looking for squirrel proofing our bird feeders and came across a video form cab7 (   • HOME MADE PVC bird feeder pole  ), we made some modifications form his design and it has worked great.
The key is for it to be (the feeders) more then 5 feet off the ground and 7+ feet away from where they can jump from.
The 4X4 is 10' in length, 2 feet in the ground with some cement. The PVC pipe is 6" X 8', Cross pipes are 3/4" X 48"
Thanks to cab7