Heres a little work on the back. I also got rid of a bunch of spikes the mesh had accumulated at the bottom of the mesh. I tried getting it back to sculptris, but no luck. The decimated mesh crashed sculptris everytime I tried importing. I was tempted to use gjpetch's sculptris file, but the details everyone put in were too lost for me to feel comfortable working with it.
My ztl and obj can be downloaded here