The book of FFR says to use this 5/8" half round rubber seal between the top and the body. After all the mocking up, sanding, fitting and so forth, I have decided there must be a better seal out there for this application. Mcmaster-Carr has a bunch of different seals on their website. Has anyone found a good solution to this sealing issue? I think a one piece seal would be a better fit but not sure which one would work. Feel free to chime in with your thoughts... thanks