Hi dsicart, I'm glad you are liking MoI!

Just in case nobody is able to modify the script as you are asking for, your next best be would be to use the trial version of Rhino - load your 3DM file into there and then select it and run Rhino's Analyze > Mass properties > "Volume centroid" command. The centroid point will be printed on the command line and you can select it and use Ctrl+C to copy the text to the clipboard.

Another helper program that could be useful for this is ViaCAD 2D/3D which is not expensive and has some various tools in it like this that MoI does not have quite yet.

- Michael