As far as I know, the center of mass calculated by the eigenvalue analysis only takes into account the applied masses (dead loads). So if you want to include all loads, you can define a fixed node (preferably at the origin), couple all support nodes to that single node, and calculate the center of mass by hand (Mx/Fz=ey and My/Fz=ex).
Here’s an old post on calculating the center of mass:
Best regards
Frederik Höller
Your SOFiSTiK Support Team