I made a new blind last year. I'm 5'11" and cut mine at 39" tall and 9"x22" (height and width). It works well for me and my 11 y/o daughter both. I have old computer desk chairs in my stand that adjust up and down which make it possible for anyone hunting out of it to adjust for their preference.
Also, figure out how you want to do your windows before you decide on the height and width. I wish I would've looked around more before deciding on mine. Dickinson Feed has some nice framed, sliding and hinged plexiglass windows for a reasonable price, but I didn't find those til after I cut the holes in my stand (which ended up being too big for their windows). We used them on my dad's stand and are very pleased with them. Don't know if you live anywhere near there...