I may not be the right one to ask. I do not ride real hard, but I probably do demand more from my RT suspension than a typical "touring" rider. I weigh 180, rode two-up only about 10-15% of the time, but had my 2010 springs set on #5. There were others that set theirs by the book, and were well satisfied. From the information we are getting back from the aftermarket and 2011 shocks/springs, the spring setting (or rating), has less to do with the body roll than the damping of the shocks. You can compensate somewhat with a stiffer spring, but there are limitations.
All those weasel words aside, I would probably start settings on a 2010 one step above the factory recommendations, and go up or down if you feel it is necessary. Remember, high settings (stiffer) give a less comfortable, less cushy ride, but reduce body roll in the corners. A softer setting will save your behind, but causes more leaning. Your cornering technique, and carrying a passenger also has a great influence. It is your choice which you prefer. You can't really have both...although with aftermarket or 2011 parts, you can come close.