I have grandiose plans ... The stair well from the main floor to the second floor were the bedrooms are in my house opens in to a huge cathedrral ceiling area. At its highest it's 20 ft in the air. I'm thinking this would be a "most excellent" area for the kitties to go vertical. For the most part they wouldn't be more than 10 ft above the ground / stairs (stairs go halfway up then reverse on themselves at landing) only place I would be hesitant about is the far wall were if I were to put shelves all the way up they are looking at a decent drop. What is highest safe height for this kitty shangri-la to go to?