It seems you need to relocate the co-ordinate system to get the section properties about the cebtroid. Also, do you know if AutoCAD mass properties will work if there are holes in the section?
Massprop works on the area enclosed by a closed polygon. If you have holes in the section, what I do is to open the hole and the outer boundary about 1/10,000 of a unit wide and add line segments joining the areas, then making sure the polygon is closed. The section properties of the microscopic sliver of material you added is too small to matter. You can relocate to the centroid if needed (Massprop gives you the coordinates) but it is not really needed.
Back in 2005, IFRs remebered to mention the step of creating a Region before running MASSPROP.
thread404-135286
You can use the "subtract" command on regions to subtract one from another to creates holes as desired, then run the MASSPROP command on the resulting holey region.
