I love this catapult model, but had an issue where it was launching items nearly horizontally. This was easily fixed by moving the location of the ‘stop bar’, making it so I'm launching treats across the room rather than right at my cat. The original stop bar location has been kept intact so now there's two options. This thing is surprisingly powerful, I can hit a spot 8 feet up on a wall from about a 15 foot distance. When playing with my cat I give it a quarter pull or less and sometimes it's still too much!

It can be quite difficult to get the pieces to snap/force fit together regardless of material, a rubber mallet does the trick quite nicely.

While tinkering I also made a print card option if you want to give it as a gift, the sprues left after cutting them out can be cleaned up with a little heat or flame. Both versions are in the 3mf file on separate plates.

Any material I've tried works well. I imagine PLA might lose some tension over time but to be honest it's so powerful as is that you may be happy with that.