Pulled a tube, and found precisely what I hoped to... simple o-ring under the crimp.Strokers and MSPs will be quite straightforward to build. It's going to get diverse here.
The bore may initially have light scratches. My approach is to first make them more visible by polishing with 1200 or 2000 grit wet/dry using runningwater to flush......should only take 30-60 seconds worth using a foamrubber mandrel (sandpaper wrapped around and taped to it) fastened tothe end of a rod or dowel and powered by a cordless drill. Then get rid of the scratches that are troublesome with 400/600 andfinish off with the extra fine grit.The piston body is aluminum also so special care is needed so thatthey DON'T make contact. A good fitting o-ring will take care of thingsat the front end, while a wrap of .020 teflon sheet is used at therear to take side loads from the pump linkage. Unfortunately I do nothave a pic of the piston assembled to show this detail.