Dynamically, as in during the game running? So like leg IK?
In that case, the ShapeConstructor methods wouldn't work. That's for configuring the shape to your needs before spawning. Once it's created, the ShapeConstructor methods don't affect it outside of reloading.
To manually change bone positions in code during runtime, you'd need to look into the animation code in ShapeInstance, and the HandsOff mask for bones. That lets the bones be animated by code rather than animation sequences.