You probably had 2 or 3 people up there at once installing stuff when it was built. I've walked on every one of ours. Sure they flex a little, and some more than others. If you're concerned, stay towards the edges. Do you have a ladder installed? If so there's your first clue. Also, you cannot do proper roof maintenance as required for warranty if you don't walk up there. At least on mine you can't.
Sent by ME
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.