I make mine with a full 4' inside dimension x 6' because I am also fairly tall and needed a little extra knee room and the extra 7" is enough. I build mine in 6 pieces, 4 walls, base and roof that can be screwed together on site. Put up base, 4 walls and drop roof over top. I use a trailer door and put rubber stall matting on floor. This is my last build, affectionately known as "the condo".