CoM correction

I am creating an AnyBodyModel for based on the StandingModel template.
For simplification i excluded both arms and one leg completely.
Now i would like to show the Center of Mass of this model, how can i correct the error in CoM position induced by the excluded body parts?

Thanks in advance,

Dear Belinka,
I would recommend to leave both legs on the model. You can exclude muscles on the second, but that will not affect the COM.