We've been testing in the UK for some time - when I say testing, it took us one run to know they were better, and they've been on the car ever since!!
The problem we highlighted was that the car doesn't centre well off the turn. It tended to hold a line, meaning you had to stay out of the throttle for longer waiting for it to straighten up. Clue came when I put some springs (AE 0.020") under the flex plates (by locating them using the tweak screws) and tried that - instant traction, and easy to apply the throttle early. The springs helped to return the pod to centre faster and more accurately. I then made some carbon plates, but screwed up on the thickness! Jason, as usual, came to our rescue.
The thin CF flex plates work well in Mod and 10.5. No tweak screws needed. We run them in the long position (I run an R drilled for RR flex plates and with the shock set back 6mm, and team-mate Jason runs an RR) and never change them. I run LiPo, Jason runs 4-cell - they work for both. Not only are these plates soft enough for traction, they return to centre more accurately.
We run GT and Duo carpet with different additive (Speedtech) to you guys, but the effect seems to be the same as Showtime has experienced - the car is just more precise.
IMHO fit the thin CF plates in the long position and use them - no need to fiddle with other settings any more. HTH