Thanks for the suggestion, Dave.
Today I cleaned the entire length IOf the that channel with a Rolodex disk. I found solid metal and no issues with rust. Think your suggestion coin codes with my thoughts: clean the channel, epoxy prime, squeeze seam sealer into the seam, then paint.
Am going to try to be careful not to completely cover/bury the seam until I find out what was originally done by the factory. This is a DD but I’m trying to keep it as original as I can.
