I just wanted to report that I sent my GTI 2500 in to Garrett to be re-calibrated for the new 9.5 coil. I sent it with my old white, 8.5". coil and when I got it back they had replaced that coil with the new 9.5" and a new, black, composite lower stem. They, apparently, put in a new chipset. Prior to this, I could not set my coil down onto a cinder track around a football field without the detector going bonkers but, now, I can lay it right down on the cinders and it acts normal. As far as depth increase, it might detect, slightly, deeper. I, recently, dug up a walking liberty half at 7" and a barber quarter at 8".
The detector did register those depths, correctly.