Find the CG of My Tricopter

This instructable is not doing something, I already done it, but I need to know the CG (center of gravity) of my tricopter, hope that you as the instructabler can help me.

I made this tricopter in Y configuration, as shown in the diagram, the axis distance of m1 and m2 is 27cm, the axis distance of m1 and m3, and m2 and m3 are 33cm, as this is not an equilateral triangle, the CG must not in the middle point, and the axis m3 is more heavier, so I need to know the correct CG position to perfect balance it and mount the flight controller over the CG point.

I also give the axis weight (with battery included), m1 is 231g, m2 is 219g and m2 is 296g, I have trial flight it found no significant trouble in CG, but it should have significant effect when the arm of m3 changed, it must has a method to locate the CG in this configuration.