I'm just building a new house for our three Kunes.
Their old ark had an 8'x4' base but the slope of the roof panels means they don't get the full benefit of the floor area. The new house will be based upon a 6'x6' floor on three runners with vertical walls and a flat roof, so no height limits.
Not only do they gain a bit of floor area they also get more volume.
Cost of the timber came in at under £100, which was pretty good I thought.