I recently purchased my first star sizer here. I decided to add an air cylinder after much reading here. I found a piece of 1" brass round stock kicking around & decided this would be my piston. I cut 2 grooves in it for "O" rings to seal against the tube wall. My question is how much resistance should I have when moving the piston in the tube. The tube ID measures 1.082", my "O" ring mounted on the piston measures 1.100". I can insert it by hand but it is fairly snug. It takes 10psi to get the piston to move on a completely clean & empty tube. I figure I can always put it back on the lathe & cut another .005". I thought I could use the hycar washer outside diameter as a rough guide. Thanks in advance.