I played with a South West for about three years and had a Predator shaft made for it. I loved the hit, but the only problem was that the Predator shaft weighed less than the SW shafts, and this moved the balance point back about .5".
I also prefer a cue with a thinner butt than the SW, so I eventually traded for my current Mottey. The Predator shafts for my Mottey cue match the weight of the Mottey shafts, and it is the best playing cue I've ever had.
I say you should do whatever is best for you and forget what others tell you. If you prefer a Predator shaft on your South West, by all means use it.