I really enjoy my coil setup on the rear. If that helps any.
With a standard SPOA I did not see much body roll, but I did not have a nice soft ride either. For 31" tires with a Spring Under you are looking at a set of Calmini springs. While they work great and make your rig nice and stable they will ride a bit rough. There really isn't many ways you can get around the rough ride without some serious suspension work, the short wheelbase and need to lift for tire clearance is a recipe for problems.
If your willing to do some fender trimming you can fit the bigger tires with less lift. I ran 33"x12.5 with a 5" SPOA, it did require the rear fenders to be cut out. With the front fenders trimmed I have room for 35" tires without rubbing and the front end is slid forward 2" for a softer ride.
tuxbaby has a nice build for comfort and ride. A 1.6l engine for more power and the shackle reverse, which gives you 2" of lift, and 30" tires which is more then enough clearance for 90% of the trails you will run into.
I hate to say it, but as a DD my Tracker is still a better choice then my SJ. Just for the extra room inside and more base power. While a Sammy can be made pretty nice it will never be a sports car with 33" tires.