Ok tested a bit, gonna update the modelviewer in some hours...
Check the tooltip for values:
New version is online!
http://www.wowinterface.com/download...o.php?id=18079
It allows you to manipulate the model to check what values work best.
@nightcracker
Saiket is correct. A SetPortraitZoom value of 1 will focus any model available to show the face unless the SetCameraDistance value is not that much out of place.