I’ve uploaded a new file, if you want to check it out. I made changes to the palm twist and the fingers. I’m not sure the exact problems you have but the rig now should be more correct. The palm twist was a decision I made based on how the forearm behaves, but I think ultimately, the twist should be neutral with the palms facing down, for this rig, where normally, it actually would be neutral with palms facing forward.
Anyway, try it out and see if it works better. Otherwise, please let me know the exact problem. This feedback is useful, since I don’t personally use the CAT rig.