Standing height in the center, stock, is 5'5.5". We built up 1 1/8" from the floor (1/2" Polyiso, 1/2" CDX subfloor, 1/8" finished floor) and came down 1/4" from the ceiling. The luan on the ceiling is screwed directly into the metal ribs. call it 5'4" finished standing room.Great clean build! Can you give an estimate of the final standing height in the back?