-- Last Updated: Feb-16-13 12:38 AM EST --
... back when I paid attention to such things (and I haven't looked at a camping-gear catalog in ages), the diagrams showed the people alternating which direction the head and feet were pointed, JUST LIKE SARDINES IN A CAN. I remember that the diagram for sleeping in a 4-person Timberline showed the people oriented crosswise to the door and alternating like sardines. I have a 4-person Timberline and it's great for two people lying side-by-side with their heads toward the door, especially since the length of the tent is greater than its width. I think three could lie lengthwise if need be, but without alternating like sardines. I sure hope that with four people inside, no one except the one who's blocking the door has to get up in the middle of the night to pee!
I also remember that the diagrams for some large dome tents showed three people side-by-side and alternating like sardines (no other way to fit three in a row like that), and an additional person oriented at 90 degrees at each end of the first three.