Thanks! I ended up doing the same. The more I thought about it there was no point in a seal like that below the top of the door seeing the lower section was in great shape. Looked like the only way it could be used full length was to remove the lower existing channel by drilling out the rivets anyway & I didn't want to do that. I did put a little weatherstrip adhesive at the bottom of the new top section to keep it from moving.
Both side of mine looked to be in nice shape, but boy they were hard as a rock. Had to break them out of the channel in pieces. The ones on the leading edge of the quarter glass were the same way.
