Yeah, always best to have, at the very least, a set of stumps to bowl to. Ideally, you would have a batter too as that's even better for getting a sense of the length you want to bowl. The second last ball looked a bit too much of a drag down to me. But that's not a bad sign if the ball has been getting released too early and slipping out. Dragging it down means it has been over-corrected a bit, but that's ok. It will happen. The last ball is exactly what you want to see (looks like it drifted a little bit as well). The arm is high but that's not an issue if it is coming out nicely and spinning. I'd only worry about getting a lower arm if the ball isn't spinning. Not every legspinner needs a lower arm. A high arm is better for accuracy, so it's no bad thing at all. I like how upright the whole action is as well. I wish my action was as upright as that. The head position is fairly steady throughout, which is very good. All in all, I'd say it's simply a question of bowling lots and lots and grooving that action.