[J P Stein]

I've had the issue of rear end stepping out during AX corner braking.
You've got everything on that car of yours so I'll assume you have an adjustable proportional valve for the rear brakes. Keep backing off the rear pressure till the rear brakes work in concert with the engine braking, mark the spot, then return it to the normal position when the AX is over.

Back in the day when I was having an in-curable push, I liked the back end to step out under braking. It helped the car to "dirt track" around the tight stuff.
This was fine when I got it right, but doing that consistently is a bridge too far for me.
I do know a 911 AX driver that can pull it off and he is bloody fast. That makes one think the 911 needs to be AXed like that.