Ed at ez-slalom recommends a 4 foot section of the same diameter PVC pipe with caps glued on, then attached mid-span to your turn ball arms with large wire ties. I did that when I put my cable course in 5 years ago, and it is still working great. Actually, mine are 42 inches since I had 6 pieces of that length after cutting my pipes building the course. No sag, and all buoys float the same. You do this, you will not need to do anything else, so long as each anchor line is about the same. No other extra junk to deal with.
For your two anchor lines at the ends of the course, Ed recommends using at least 4 feet for every foot of depth. That's all you need. And, use 3/8 or 1/2 inch nylon rope. The nylon rope will last forever, and is slightly negatively buoyant - won't float up on you.
Plenty of ways to skin this cat. Keep it simple.
Good suggestion above to have hooks on the top of your buoy anchor lines for quick attachment and removing.