I still don't see the benefit to using cross tees on top of the pole. I still think connecting the buckets in a series would work better. I could see putting a couple of tees between two buckets for cross support. You could change the existing tees installed above the buckets with cross tees and connect them for some support.
As for UV protection of PVC pipes here's what LASCO has to say about this.
http://www.lascofittings.com/support...gPVCPiping.asp
Instead of painting the PVC pipes I would think you could use this instead -
http://www.amazon.com/303-Products-3...otectant+spray