Andrew, If you have the pose in which the legs are how you want already, then you could open it in a text editor or cr2edit and delete all the parts that you don't want to modify save it as a .pz2 and name it whatever you want in the pose library. When you load it in your figure it will only modify the legs and will keep the rest of the body intact. This is the same process to save a pose with my NBS.