You can take a wrap or two out of the coils up front and go to a 3" block in the rear, but you're not going to get much lower than that without major mods. Remember it may not seem like it, but you have quite a bit to put back on that car before it is at curb weight. May want to wait and see where it winds up. You may be surprised.
If you do a 3" chop (perfect for that car IMO) then you won't need a second roof. I would recommend moving the entire roof forward to line up the A pillars, then after you massage the sail panels put a filler strip across the top of the above decklid panel. This effectively shortens the roofline as you bring it down, slightly shrinking the quarterwindows and lengthening the trunk area giving the car more of a business coupe profile than a sedan. It works out nicely...