I also found it to be impossible to create a new set of item capabilities. I wanted to use a different style of thrust animation only for seaxes, but it still used the list of animations for itcf_thrust_onehanded. Even when I gave my custom itcf a different hex value it made no difference, which doesn't make any sense to me. I can't see how it still knew to use the itcf_thrust_onehanded; I'm certain there was nothing in the items files or animations file to point it in that direction, so I'd have expected it to either work or crash.