Agree Re oring type ,round should work ok.NBJust a word of warning re these leaking shafts..If this shaft leaks, water will go down and sit on the plastic 4 screw plate inside roof.Water will then penetrate the ply and get under the white plastic coating with resulting delamination.Wiped some epoxy into the ply .In other words you may have a leak and not even be aware .Would be exacerbated if aerial rotated a lot.