Bruce- I hunt three in my blind, but I will admit that my preference is to hunt two.   I divided the 8' length into three equal parts, and spaced the braces inside the blind so three hunters each have their own space.  I used ideas from the commercial guide hunters in my area, and made my blind a little bit bigger.   The commercial guide outfits make the pit blinds narrower, and hunt four per pit.  They usually place four pits in a row with 20 to 30' separating each pit.  They use the sliding top, and I used that on my blind.  
My pit is on a hill, so I do not have any water issues.  I do also have a wood floor that I built using hardwood pallets.  I did modify the pallets to fit better, but it is nice not to have a wet or muddy bottom.  I use a heater when an older friend of mine hunts with me, otherwise, I keep things pretty simple.  I shoot a lot of geese each year, but I do hide some of my decoys when I'm not hunting so the geese don't  get to smart about my pit location.  The guide outfits do the same, they leave a few decoys out when not hunting, and set out all the decoys each day they hunt.
My pit is on my farm, so I had the luxury of making it as large as I wanted.  It is very comfortable.  Most days I only set out 12 to 18 decoys, half motion decoys, half big foots.  Late season I add shell decoys on the outskirts of the decoy spread.  Seems to work . . .
Good luck with your blind project, happy to share any other details.
Miller