I was rushed with my initial response, so I'll try to explain this set up and what I've learned from others. From what I can tell, none of the 28" tires require a lift kit. Vertical clearance is not a problem to run 28s. The larger 28s (Roctanes) may rub on the rear of the fender well, forward a-arms would be the solution for this. Same with most 30s, I believe... if you have forward arms, you can run them with no lift. You may need to do the rear arms too for 30" tires. I'm not 100% sure that you'd need a lift to run 30s, may be able to run them with just the a-arm replacements (again, not 100% sure on the 30s).
With the Carnivores that measure 27.5" like mine, you won't need forward arms or a lift kit.
I'm most likely going to remove the highlifter kit from my ride and bring it to the Takeover for barter. I want to keep my CG as low as possible, and removing the lift kit will give me back some travel and soften the ride even more.