We have a 2010 Passport 300BH...right after we got it home last year, a recall notice came for roof seals (caulking?), not sure right now. Took it to the dealer, they just walked right on it to inspect everything (it passed).
I have been on it once to inspect myself and give it a thorough cleaning.
I think the construction is meant to hold your weight just fine.
Hope this helps!
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2010 Keystone Passport 300BH
2006 GMC Sierra SLT Crew VortecMax 6.0L 4:10's
Husky Centerline / Tekonsha Prodigy P2