I'll defer to Nick's experience on that, but my knowledge of levelling kits for stock vehicles is that anything over 2" is usually where the corrected UCA are recommended. You can always ask JBA about their stock geometry UCA and if it would work for a 2" lift.
I'm surprised that with a 6" kit with the front strut spacers that you would need to still go higher to level out. I almost wonder if the installer used the rear 5" kit when they only needed the 3" kit or something.
@JB1 I think used the BDS kit and might know better than me if there's a misconfig or why it feels like you need to go higher to level.