At our camp we have about a doz or so. Most of them at 4'x4', they are to confined with a chair inside when trying to stand up, move about whatever.
I built mine 6' x 6', 12" window openings, and put her 8' in the air on pressure treated posts and frame, carpeted the floor, and swivel office arm chair. Advantages are lots of room to move around if your taking a coat off or the like, QUIET with the carpet, QUIET easy direction view change with the swivel chair. Plastic javex jug cut to suit mounted to the wall with plastic tubing running down to a depression in the ground suffices for the #1 nature calls. Works like a charm, have shot many deer from it.
Build it big, with small numerous openings on all sides, so you can block the wind and to conceal yourself as much as possible as deer and moose do look up especially if they see the slightest movement and human shape. Carpet on the floor and a swivel chair are essential to help eliminate noise. Get it up where you want it first thing in the spring and clear shooting lanes before the leaves get on the trees and the bugs get out. By the time fall roles around the animals have had all spring and summer to get used to the new structure in there back yard and are used to it.