My brother has a 3 wood Callaway VFT regular. He'd like to reshaft it.
From what I gather, Callaway are borethru, with no need for a ferrule.
If I reshaft with a regular aldila (or maybe prolaunch, I still haven't decided yet), will it become stiffer?
You need a ferrule. It's a specialty one too. A sleeve that inserts into the head of the club. See Golfsmith for details, they're all labelled accordingly (for VFT woods, ect). .335 and .350 available.
The shaft will become stiff. CK and I had a long drawn out argument about this. OEM shafts that are labelled "stiff" are in fact regular. And X-stiff are stiff. If you want a stiff shaft, insert a regular. With Adila, I think you can tip trim that as well to stiffen it up even more. Grafalloy doesn't ask for stiff tip, as they are stiffer than normal to begin with.
Golfsmith also has trimming instructions for almost all OEM clubs, including the VFT heads by Callaway.