Alright so here’s the current state of the vertical jump test pole:
So I’ve got the two PVC pipes, but instead of one being nested inside another one I attached a shorter section to the top of one pole with duct tape. Then I threaded another pole through the short section, and that’s the pole with the arm on it. The pole with the arm on it is the one that can be raised and lowered to adjust the height.
Here’s a closer photo of the two pipes next to each other, where you can see the height measurements. I drilled a single hole and put a small wooden dowel through the “adjusting” pole, then measured the distance from the bottom of the “base” pole to the arm at the top of the “adjusting” pole. The plan is to have the dowel in the “adjusting” pole fit into a series of holes on the “base” pole, so the lines denote where I want to drill more holes into the “base” pole to get the corresponding heights. I went with two-inch height increments from 8 feet to 11 feet. One-inch increments didn’t feel meaningfully different from each other, plus I was a bit worried about the sturdiness of the PVC with 36 holes drilled in it all on the same side.