If you add an air tank, the ride will be smoother.
That is because the total volume of air will be larger, and so the air will compress easier, because there is more of it.
Running direct lines from the compressor will give a firmer ride, as you have now.
You can also put solenoid valves between the tank and the bags, with very small lines going around the valves, and so make the ride stiff or soft, (switched) completely independent of the ride height.
Very cool car.