Most campers will hold one person walking around to do maintenance and inspections. Watch your pressure points though. If you are going to be kneeling in one spot you should put a piece of heavy cardboard or thin plywood under your knees to keep from denting the plywood under the roof.
N E V E R put lawn chairs up there to sit on. The rubber membrane can tear and the concentrated pressure can crush the roof structure.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW