I use 8sinn cage with the (i think its called) scorpion top handle, got 4 hot shoe mounts in the handle plus screw mounts all over. With rails under the cage, i still have not managed to get a perfect balance. But with monitor placed on the back hotshoe on the handle, hip shooting is a breeze and very stable, but going one handed low is a tad too shaky for me.
I am currently looking for the classic Juicedlink RM333 (anyone know someone?), to be placed on the back end of the rails for a uniform front/back balance. Because adding a shotgun at the moment throws of the balance and having a zoom recorder under or on the side is just not working. (Plus they have the worst battery life and syncing is crap).
I am trying to increase the cameras “momentum” not sure if that is the right word, but the bigger the rig, the smaller the shakes, but too big and it becomes cumbersome, so its really about finding a balance between how heavy and balanced I want it.
I would just becareful about making your rig too wide, rather I would lenghten the rig for better movement.