I have a Valley Engineering PRSU on my VW powered biplane. I need to find out where to get replacement balls for the belt tension-er. They are like super balls there are six of them. I also need to find out how tight to put them, there is supose to be two marks to line up, but mine only has one with no line to line up with. I am not sure how far I can twist these balls out of shape without damaging them. These balls must be used in some other application. They look like maybe silicone? Thanks for any help.