Just wanting to touch on something here. Does it really make sense for a grappling hook to reach a place beyond its length and then leave the thrower's/shooter's hand, making the hook stuck and unreachable?
Seems a bit over the top to me, personally. Anyone with common sense wouldn't let go of the end. A hook reaching a height beyond its length implies some baka just threw it without hanging on.
That said, -maybe- it isn't unlikely if you're dumb as a box of rocks. So if it isn't already, I submit the following:
Add intelligence/agility to whatever stats already govern hook throwing. Smart people should know better, and agile people shouldn't be fumbling like that.