I made this using PLA+ at 5% infill density and it works fine. I'm using Staples brand #84 Rubber Bands and Hillman brand machine screws that have the item number 7671 (they're about one inch long). I tried using 3D printed screws for the piece that takes the most stress but they broke so I resorted to using metal ones and it works fine now. This isn't a 100% on model reproduction of Usopp's Kabuto, more like an interpretation that's a blend of the slingshot he uses in the beginning of the series and the Kabuto which he gets later. The base piece takes about 5 hours to print, the lid maybe 2 hours, and the "baller" piece takes one and a half. You'll need 4 of the "bolts" which each take around 15 minutes (these are to secure the base piece to the lid piece) and 4 of the "Band Holder" pieces which are meant to protect the rubber bands from directly rubbing against the metal machine screws.