That is very nice work. Well done xSlingshot/Catapult/Catty ...
Whenever I’m out I have one in my pack, camping Bushcrafting etc.
I bought one off eBay approx 8-9 years ago out of wood. When it arrived it looked awful it needed some finishing off and I felt I could do better.
So Christmas was coming up so I made a few for family and friends. Since then I’ve made quite a few basically from scrap wood and cutting from various peoples projects.
Looked at round bands but for me flat bands are the most versatile. My reasoning is quite simple, you cut them to any length any width and by tapering you can increase the speed for a given length. By choosing a lower powered band you can concentrate on accuracy and consistency. Once you have that then just add a smaller band in tandem to increase the power and distance.
Ammo, my preference is 10mm nut which I shoot into a padded box. On ebay you can buy clay ammo balls which clearly degrade without issue. Ball bearings are the best for speed but can ricochet so heads up.
Hopefully I’m able to upload a few pictures.