Knocking someone out safely isn't cheap. There's a reason anesthesiologists are so highly paid. Just ask the hostages from Dubrovka Theater [0] how improvising an anesthetic gas can go (spoiler: you'll need a medium/ouija board).
In theory yes because you can use the space at the top that would otherwise be above people's heads. No guarantee they get to their destination alive though.
Once you include space to get people to the restroom though and to allow them to breath during the flight I think you get a higher density while standing vs laying down.