So, we got my nephews the pathfinders trebuchet kit for Christmas, but since we were seeing them for thanksgiving, we gave it to them today and constructed it. It works amazingly well, shooting from our front porch, across the yard, and landing a grape tomato on our car on the side of the road. Here's a video of it empty firing inside the house.
https://youtu.be/LbT_eFciVvM