I have played with a predator shaft on my Scruggs custom cue with a cocobolo joint, on a predator sneaky pete butt with a SS joint, on a predator all black butt with a SS joint (I think the 2k1), and just recently I switched to the Z shaft on the predator break cue butt. Each combination was at least for one year, except for the last which I just switched to a couple of months ago.
In my non-expert opinion, the deflection characteristics of each of these combinations was about the same. I didn't have to make any adjustments when I made all of these switches, except a slight one for the Z shaft (all the others were 314 shafts). The hardness of the hit might have been a bit different with each cue, but you can probably make that feel anyway you wish by switching tips.