The "group" command in the set-up room does a poor job at guessing. It's like those auto-tune buttons on car radios; good for finding the nearest top-40 station but really poor at helping you tune in to the stations you want to listen to. You would be much better off grouping manually, and rigging manually. The tools are there. The tutorials are available on-line -- many of them at Renderosity either in the tutorials section or referenced in older posts in this forum and others. One thing; in the opinion of most people "slicing the mesh" within Poser itself is a fool's game. Your modelling application is likely to be a better choice. Use Poser for adjusting the joint centers and other parameters only.