calculating vertical center of mass.

I need to calculate the vertical CoM for a stack of rigidly connected masses. For the sake of this argument the masses are evenly distributed horizontally. The actual object is a bar table made of various materials from the ground up. I need to eventually calculate tipping force. I understand about center of mass not moving past the point of rotation. I have a large cast iron mass near the bottom. This should lower the CoM to the point where more force would be needed to get it out past the point of rotation. It seems like it would be stable but I'm at a point of significant investment and don't want to commit on a "seems like". So, help