Did you look at the solar roller coverstick that I am currently using? www.solarroller.com

For my previous system of rolling the cover pieces (I cut the cover into fourths), we used 1-1/2 inch pvc but it doesn't really matter. We made the clips from slices off the end of the same size pvc. There are some pictures in one of the links above. Did you see them? (Post #4 above.)