Deepcut said:
I have a pretty good understanding as I am a pilot (private plane) and also a bariatric surgeon. Weight and balance is critical for flying and experience allows you to just know (from many previous calculations), that weight and balance is not an issue. Other times needs more distribution by moving largest passengers forward/backward. It is important to be discreet and explain safety aspect of proper loading. I ask my passengers (wife included) "weight including your carry on bags".

As a bariatric surgeon, I can typically estimate weight very closely, especially larger people. I also know how often my patients report being hurt by insenitive comments, especially in public.

As a sailor, we face the same weight/balance issues , usually when getting into dingy... however this is evident to all and passenger tend to distribute themselves to balance the "ship" without much instruction.