To the best of my knowledge, and I've done a lot of asking and searching, it's currently not possible to only calculate the mesh for one or more specifically selected parts. If I generate the mesh for my model, then decide to change the mesh settings for a single part, SimMech currently has to re-mesh the ENTIER MODEL just to create the new mesh for one single part! This is completely unnecessary and time-consuming. Please allow me to select specific parts and only mesh or re-mesh those specific parts.