You do realize you have to cut massive amounts of sheet metal out for Rocket Bunny? You shouldn't have any problem slamming your car if that's what you want. I'm running 325/645-18s and while I don't set my ride height low we most certainly compress the suspension under race conditions way more than that.
Also here's a picture of how much we ended up cutting out of the fenders.
How much you cut out will ultimately determine how low you can go. I would make sure you work with the body shop or whoever is installing the RB kit so they can cut out and then seal what you need to clear your wheel/tire/ride height combo.