In calm lakes, 12ft is plenty for 2+1. I've had that many on my 8-footer
many times, although 12ft adds some moving-around room.

Seem like a small boat can do well if the water is calm. If what you
said is true, I should be able to fit 4 adults in a 16-ft boat
(combined people weight is around 700-lb). But I expect to use the same
boat in both calm freshwater lake and protected sal****er area where I
may get some waves from passing boats. I probably need a boat that is
slightly bigger than the minimum -- something like 17-ft or 18-ft.

Thanks for the info.

Jay Chan