Aloha - I have an Old Chap button filler thats gotta have a new sac. I've installed a number of sacs in lever fillers. This section is stubborn. When twisted, I get a tiny bit of daylight between section and threads. It revolves rather freely for a few milimeters and opens just a hair, then locks tight. Pulling straight out gets me nothing. Am I pulling against threads? I really don't want to damage the extra nice pen with a wonderful flexy 18k nib. Does anyone know if the Old Chap sections are threaded or friction? I'm soaking overnight in Windex/water 50/50 solution at the moment, but I don't know if I am working with a section with threads or friction.