You're not building a stand! You're building a house!!
The stands we used in the hunting club are 4 x 4, and use 2x2 framing on the corners, built on 2x4 floor framing. Most use the plywood flap cut out for the window opening as the closure, with no actual windows (usually 12-15" high, 18-24" wide, at eye level sitting down). Same for the door. Sounds small, but it's really just about right. Get it too big, you just have a bunch of extra air that has to be heated (hard enough to keep a 4x4 house warm). The only reason I can think for a 6x4 or 8x4 would be for two people. Depending on how high you are going to place the stand, anything over a 4x4 gets real heavy trying to move and erect. If you put some type of real windows in it, you have to make sure they ALWAYS open effortlessly and without sound. Something we've never managed to find. And, if you are going to keep the windows/ports open while hunting, flaps work as well as windows.
The main drawbacks to the ones club members build (not me) is that since the roof is often only tin roofing, they often use nails that are too long, and you have to be careful standing up! Definitely want the roof high enough to stand up in. Old office chairs are great, especially if you put down a layer of in/out carpet on the floor to dampen noises.