I think the reason the wrists move around so much on the nail - more than mine do - is not the difference in the figures we are using, but that you place the nails farther up her arm than I do. This has to do with the location of the goal point for inverse kinematics, which is the point Poser, and I would image DAZ Studio also, hold stationary while performing IK calculations. That's what IK is all about, holding the goal point stationary and calculating the bends and twists of all the joints in the chain to make it happen. That goal point is somewhere in the palms of her hands, while the point you really want to hold stationary, the location of the nails, is proximal (up her arm, in her wrist) from that. My placement of the nails is in the heels of the hands, yours is somewhere around the joint with the radius and ulna bones. Your nailed point will move more than mine.
To make the nailed points remain stationary, you would need to edit the IK chains and change the goal coordinates. I have not done this, kept putting it off for another day, but I know that's what it's going to take. In my case, it means having a specially modified version of V4 (actually Stephanie 4 or S4) to use when she is crucified. Maybe you would have to create a modified version of V8 you use only when she's on the cross.