Thank you all.
This is definitely cool and dangerous enough on its own that is should work. It should even work more then once.
The crew will have to hit the right spot of course.
I am not worried about the launch but the landing is kinda sticky.
If the throw him 500 feet that could be as high a 250 fall. Even a 19th level monk will not ignore that (other then just sucking up the HP loss).
I know the player does not mind being hurt by this but he will want to be able to function when he lands. He may be okay with I take the 6d6 damage the trebuchet would do and go from there.
I am leaning towards the falling damage being the however far down the mast he needs to go.
From there the real issue is the horizontal speed.
Some one mentioned using a grappling hook and swing around in the rigging.
How about a standard action grapple the crows nest as it come near and an acrobatics check to kill your horizontal motion. DC equals 1 per 10 feet traveled in the air? That is only a 20 for 200 feet and 4th level character should be able to pull that off. I have seen DC 50s be common place for well honed skill by the early teens. That would allow 500 feet of travel
This would allow the monk to get there safely in all likely hood by the round of swing around will give the crew a chance to act against him.
