Not to be a smarty, but there should be a recommended weight limit sticker on the bulkhead, er wall, at one end of the over cab bunk. My 2006 has a sticker hidden behind the curtain on the driver side that refers to a suggested weight limit of 250 lbs. The ladder should be able to handle that. Now, that being said, most engineers build in "Murphy factor", as in over engineering the strength. The fold out couch may be easier to use. My mom in law is a spry 75 years young and would use the couch if she ever went with us.
Chris in Virginia
2006 Sunseeker 3100SS/LTD
2008 Smart Passion Cabriolet TOAD
1986 Honda Helix (Original owner)