I've created a spit assembly using save bodies in a master part model.  I checked "Derive resulting parts from similar bodies or cut list" because there are several duplicate bodies created with mirrors and patterns.  The resulting split assembly is correct, but if the master part model is edited in such a way that the bodies are moved around in space, the resulting split assembly does not update correctly.  The locations of the parts don't follow the mirrors and patterns of the master part file.  I think this is because all the parts are fixed in the assembly by default.  It appears that the work around is to not use the derive resulting parts function and create mates and patterns in the assembly file.  However, it seems like a big oversight that the assembly can't update to match the master model.  Does anyone else have this problem and is there something I'm missing?  Ultimately, I want to create an assembly file that can be easily updated via a master model without problems.