First, see if you have any issues with hands with your version of Poser. If not, then why bother?
If there are issues, then chopping the hands can be done after exporting BVH character from poser. Open BVH in
bvhacker. In the tree view of joints, select the parent joint of right wrist (that should be right forearm), right click and choose
Remove Descendants. Make the same with the left joints. Save changes. Then import the resulting BVH to Mocap Studio.
Of course, after chopping hands from the skeleton, you cannot transfer wrist/finger movements from Mocap Studio to your character.