I hate to come late to the party but do you have a picture of the worst leaking tube? Especially the bottom. The seal between the tube and the head has to be compromised somehow (here we go with the Captain Obvious jokes) and it has to be at the bottom. Is the bottom of the tube convex? Like it is a bit short and is being distorted when the plug is installed?

"We live in a time when intelligent people are being silenced so that stupid people won't be offended".