The long slide box drills are a great idea for getting used to jumping up with a longer run. But, if you are looking for a way to improve on jumping up higher, we do a drill that was named "jumping the crick." To "jump the crick" you can place your pole in a box that isn't surrounded by pits (hold about two hands higher than if you stood up straight with the pole next to you and reached as high as you could on the pole) and, with your pole in the box, act like you are checking your step (put the pole in the box, extend your arm up, go on your toes), and then take two steps back from that spot (one right, one left). Hold your pole on your shoulder, sliding it as you take the two steps, and jump up, while hanging on the pole, much as if you were to use a pole to jump from one side of a ditch to the other. If you easily get over to the other side, move your grip up a hand, and then another, etc. until you stall out on the top. This drill helps with getting your arm tall on the plant, jumping up, and developing a good lead and trail leg. It was also shown to us by Derek Miles