Prior to 2011 it was very easy for the parting surface built from a parting line which changed convexity or direction to self intersect and overlap or simply not go in the direction the mold designer required. To avoid this partial parting surfaces hand to be built and the difficult pieces modelled by hand with loft or other surface commands.

In 2011 if the user selects a PL feature which is a complete loop or selects a chain of edges which for a loop, then an additional check box 'Manual mode' will show in the Options group of the PM, this will display on screen controls which allow you to:

1) Adjust the vector of surface creation at each vertex around the parting line by draggin it along the preview rectangle

2) specify a start and end vertex, where the surface will be created using the fill surface algorithm

This provides much more flexibility to get the parting surface you need created in a single step

I'd appreciate your feedback on both the functiopnality and the UI