Just be aware that a panhard rod will stiffen up the rear suspension a little. It depends very much on your driving style as to whether or not you will notice a benefit. If you tend to corner fairly hard, particularly if you start to feed in throttle as you hit the apex, you will notice an improvement. If you have a more relaxed driving style you probably won't notice any difference.
Just as a little aside a panhard rod, a Watt's linkage, or some other form of lateral control must be used if coil spring suspension, such as the 5 link suspension, is fitted. Leaf springs have an inherent resistance to to lateral movement.