No, you don't balance with the fluid housing on it. You only use the hub. You'd never get it right with the fluid housing on it at the low speeds a balancing machine spins at. All the fluid housings are neutral balance. The hubs are either neutral or external balance spec.

The fluid in the housing is a high viscosity silicone based fluid. At extremely cold temps it is thicker and at extremely high temps it is thinner. It has high shear strength, though, and that is where the damping comes into play. It's not like the inner ring ever freewheels.

ATI's are fine. They are basically indestructible elasomer dampers tuned to a higher than stock rpm.

As far as blower builders not using dampers, it's because the big blower belt acts as a damper. If you run one of these, though, and break the belt, don't run the motor.

I'll stick with the Fluidamprs.