trace,
I use ACIS (.sat) files when sending assemblies to NASTRAN. They come in as seperate parts, so they can be assigned different properties. The one thing I had to do was set up the export from Solidworks to use an early version (Ver 8.0) of the ACIS kernel even though I am using a 2003 release of NASTRAN for Windows. When exporting, click on the options button in the save as dialog box and set the version back to 8.0. Watch the scale when importing.
Timelord