I went to the Apple store today and took my Smartstand with me to try with the large ipad pro. No problem, though in portrait mode, if you want to have it plugged in, the lightning port will need to be at the top. Seems veny stable.
Here are some pictures at the store and one at home with the smartstand folded up next to the textblade to get some perspective.
As I said, Amazon has them for ten dollars but the local Office Depot here has them for seven. Just checked Office Depot online and it is also seven. But the picture only shows one position for it while the one I have has two. However, the way it works, there isn't much difference. I really like it and bought three more.