Having driven yours for a good piece of distance over a lot of different surfaces, I was very impressed with the ride and handling from the C/Os.
To your point about the GTS RCK, know that the Pinks are only supposed to drop .8"-1.0", in reality, it'll likely be closer 1.25", even on Bilsteins. So don't think you'll need to deinstall your GTSpec RCK because once everything does settle, you'll likely be in the sweet spot for the RCK. You'll definitely want to get realigned though because of the static camber changes and likely changes to toe as a result.
Pro dilectione Dei et patriam