A guy I work with added two drain tubes in the rear window channel of his camaro. He just welded in an eighth in piece of steel tubing and ran rubber hose out the bottom of the trunk floor. They work pretty good. I can see some benefit of draining the channel, but I usually blow out the area with an air hose when I wash the car and call it good. If I were fixing up a daily driver I might do it. For something that doesn't sit outside very much, I wouldn't bother.
