I once built a backyard zipline for the kids and an adult tried it. Went about the same. That zipline was dangerous as hell but the kids liked it. Luckily no broken bones. I told this one dad to catch his daughter at the end (she lacked grip strength sufficient to hold at the end) and he didn't listen. The girl flipped in midair and did a full cartwheel before slamming into the ground. She never wanted to ride it again!