It would depend on the OUTSIDE DIAMETER of the shaft.
The tenon diameters are different for each shaft.
314-1 - .402"
Z-1 - .360"
314-2 - .414"
Z-2 - .385"
As you can see, if a 314-1 O.D. is .502" (12.75mm) and the tenon is .402", then 1/2 the difference yields .050" ferrule side-wall thickness.
You will also notice that the Gen2 shafts, utilizing a slightly larger tenon, have an equally slight reduction in ferrule side-wall thickness.
Plastic, suitable for ferrules, weighs more than wood.
I'm always concerned when someone requests a turn-down on a Predator shaft. This is one of the reasons that there is an imposed limit on how much these shafts can be reduced and still maintain warranty. That's why I asked the question I asked in post #11.