Inspired by an AMS comment, I've just added the following items to HandRight-Standard:
Basically the idea behind these is that you can use them to simulate holding an object without having to use masking, since you can only mask one thing to one other thing at a time. So for instance, you can use the first two to put a rifle in a character's hands with just layering -- all the parts that would be covered in the hand are just not there in the first place.
If this works and there are other hands you'd like to see get the same treatment, let me know.
