I recall mentioning a slight sag in that spot to my dealer before I took delivery in 2011. When I picked it up the sag was gone and hasn't returned. I don't know what the dealer did, perhaps straightened the extrusion along the forward edge of the lower roof, but it worked. Should be a warranty item.
It's never too late to have a happy childhood!
Lee, WU0V, and Courtenay, N0ZDT
2011 Rockwood A128
2000 Silverado 1500 pickup
60W solar system
2000W inverter generator