I have looked into this and the rubi springs are no different than the springs for the 4.0 / hardtop. The reason you guys are getting lift is because they are stiffer to accommodate for the extra weight from the i-6 and/or hardtop. They are NOT taller. The part numbers are the same no matter the model, just the engine and top make the differece. You can check, and even order them straight from the dealership (expensive way to do it tho) . But in a way this is a good thing because it allows more broad of a search and not just restricted to rubicon models. Just look in a junkyard for a wrangler with a six cylinder and a hardtop.
What it comes down to is us guys with the lighter jeeps (4 cyl and softtop ) can get a cheap lift out of just grabbing some stiffer springs made for the heavier models. I haven't done it so those that have will have to answer for what the ride quality is like, though.