Just an FYI for anyone interested. Had the Hummer in the service department today. They were going to do a water test on my roof to try and diagnose the leak. Before they started that the service manager brought out a copy of Bulletin 24-NA-029. After going through my symptoms, the bulletin...
My roof leaks at or around the front inner corners of the second row panels. No solution yet. I also have the shower when entering and exiting the Hummer.