here is a couple of shots of the solid rubber gasket that i put on my 50.

http://good-times.webshots.com/photo/2848817660099732965DQQFvU

it is a little thick and does make the vent door stand a little "proud" but with a little adjustment on the lever and linkage, it seals just fine.

sorry the pictures are sideways. forgot to edit that before i posted them and now i can't seem to get them rotated.