They will not use these sheds at a greater density than 1 animal per 6' x 8' space even in inclement weather when temps are above 90 F. A low roof does not allow effective cooling and ventilation.
Also, we have found that alpacas and llamas will preferentially stay within a three sided open faced barn that is 30' x 60' with a 20' roof rather than stay outdoors. Even on sunny days, where temps are above 30 F, they stay in the barn only coming out intermittently. They will easily stay in the barn during hot weather.
Perhaps this is an effect of 'individual space infringement'.
When they stay in the large barn, they stay anywhere from 2 to 10 feet away from each other. They tend to use 1/2 of the barn (the perimeter) for eating and sleeping and the central area for manure.
Thus, I think that social stress is based on the ceiling height and the depth of barn as much as anything. I would prefer a long, deep barn with a high ceiling.
That said, if you are planning on building your own barn, lay out your plans and then increase the size by 25%. You always need more space - for a sick animals, storage, shearing, machinery. The time to get a bigger building is before you build it. But, sometimes the budget just doesn't allow for it and you need to work on growing your outbuildings in the future.