Does anyone have one of those kneeling chairs? Are they any good? Since spending hours sat down working from home I have developed what I describe as necrosis of the arse cheeks. It's like the circulation is non existent in the fat at the bottom of my back and feels numb and uncomfortable. Don't want to buy another office chair in case it's just the same. How about one of those balls you sit on, would anyone recommend one of those??