Sub Chassis C of G

I wish to find the Centre of Gravity of a sub chassis in order that I can arrange the suspension points equidistant from this point. The sub chassis is effectively a long isosceles triangle with the arm at the acute angle end and the platter bearing toward the opposite side to this. The arm and bearing are located on a line through the middle of the triangle therefore the chassis is balanced either side of this axis. Therefore I only have to find the balance point on this centre line. I can find the C of G of the chassis easily by experimentation but obviously do not want to do this with the arm and platter fitted. I know the weight of the arm and bearing/platter assembly and where they will mount on the sub chassis. I could do a simple lever arm calculation to determine the C of G between these but this does not take the sub chassis C of G into account. Is there an easy way to calculate the overall C of G of the sub chassis/arm/platter assembly?
 
You could give me the dimensions and weight/densities of the parts and I could model it for you. Would take me 30 minutes tops. it is only effectively 2 spheres/points and a triangle as far as the cog is concerned.

I'm sure there's some clever maths to do it, but what's the point of having huge processig power and doing the sums yourself.

A simple drawing with weights and centre line positions + triangle sides would suffice.