Alright, so just to post a couple of small updates, gonna add some pics/vids later, but for now...
...the diff tuning was a definitive success! Lowering the preload to 296kg is spot on, because now it does lockup quicker, tested on the local touge a few hours ago. Where previously it had a ~one second delay until it locked up, and which subsequently resulted in a violent oversteer if continuing to press the throttle, is now actually quicker lockup with slightly more gradual oversteer so it's much nicer to throw it around uphill hairpins.
This winter I also replaced the disc rotors, as the previous (brand new ones
) got warped, so I put new EBC Bluestuff pads again, and it works very well. I think the previous pads (EBC RP-1) might've been the reason for overheating the rotors.
On the way home, got a surprise in the rearview mirror when a newer Porsche Panamera glued on my back and then did a provocative overtake. Had a go with him on the next few corners where the Z presented itself not as a decent contender, but an absolute beast. I backed off after three corners because the Porsche driver was (I believe) either a newbie or unfamiliar with the car, having had a couple of uncontrolled sways braking for the corner and ending up it the opposite lane unwillingly. That was my cue to just let him go.
Anyhow, the season has only just begun, and so far I'm loving the current setup on the car!