Balancing a Giro mount

[DRT]

I have a Tele-Optics Giro 3 TwinView mount and have just bought a 10" Newt to hang off one side. The Newt plus bits will weigh 12-14kg so is beyond the mount's stated limits for operation without counterweights.

I am in the process of ordering a counterweight bar that will screw into the hole in the dovetail shoe on the other side and I have weights from a CG-4 that I hope to use to balance it.

Is there a technique to balancing a Giro mount similar to that used with EQ mounts where you can use the tension levers to find the right balance in each direction? I can see how to do that with balancing each scope by loosening the altitude tension bolt and sliding the dovetail along until the scope sits horizontal but, with these mounts being so sturdy, how do I judge whether or not I have the right balance laterally across the mount? Is it simply a case of putting the same weight on each side (or the equivalent with weight x distance if the bar is long enough)?