Difficulty w/ Polygroups & splitting a mesh

[system]

Hello, all.

I’ve been looking for some help on fixing a mesh so I can prepare a new mesh for splitting and opening its mouth. I have tried masking the model off into separate Polygroups using the MaskPen brush and then using Extract and Group splits. But when I use the Transpose tool, the mesh between the upper and lower jaw stays attached and just stretches outward when I rotate or move. It does not properly cut along the Masking like I want it to. Am I missing any steps in the process, or am I not cutting the mesh apart correctly?

I can provide screen captures should you need them.

[beta_channel]

Pics please

[system]

Sorry about the long delay. Here are some screencaps from the project:

The first one is the whole mesh after using Transpose and the polygons not separating. The second screencap shows my two Polygroups I have set up (via MaskPen tool), and the lower jaw itself in a separate Polygroup. I am trying to separate the two, but nothing I do will properly separate the groups.

[system]

Bump back up. Anyone have any answers to my problems? I have yet to properly execute the split and I keep getting this messed up mesh issue.

I’m also discovering I cannot get the Transpose tool to properly mirror its symmetry to the opposite side of the jaw line. I’ve created the model entirely within Z-Brush using brushes. Where do I properly set things like pivot points and properly mirroring symmetry across the axes needed to just rotate the model and join it with the other meshes as subtools?