2/28/21 Got the email response and it is clear the pattern and fix I have to do. Not to bad to make this SB complete. The "??" pointing at the odd rivet is what came from the factory in that position (oops?).. Engineering said to leave it alone. I really feel for the guys that have to this to a painted aircraft 2/18/2021 A Service Bulletin came out about the attachment of the the two halves of the fuselage and the rivet pattern that connects them. The rivet pattern is not symmetrical on each side so careful counting is in order My pattern looks different from the 'before/after' descriptions so I marked the the area and have sent an email to technical with what I think the fixed should be for my aircraft. We have been moving to another town (5 minutes from the hangar!) so work on the plane has slowed to a crawl for a while.