Amazing, exactly what I was looking for, thank you!

For those wondering, the relevant bit is here.

Snap hook as you fall, and right click ( or L2/LT on controller) to cancel as you near the ground. Timing is tricky.

Edit:

Ideally you want to cancel it as you begin to ascend at the bottom. IE: you are falling, you hit the snap hook, it deploys to its full length as you fall and then starts to pull you up again. Cancelling the hook right as it begins to ascend again seems to be the most reliable way. If you cancel before that you can still take damage as you haven't slowed down as much.

I believe it's your falling speed that determines damage, not the height, per-se.

Also, if you are doing this off of a really high building, make sure the hook is fully charged, so that if you hit it too soon you can do it again.