Pat-
Switching from a 154 Hot to a 168 Vokl, and you'll feel much more "in Control."
As far as stance width goes-- for GS I personally ride 19.50 inches as centered on the board as I can get. At 5'7" I'm rather short, but even the taller guys I know are riding GS stances at about 19.50 inches to at most 20.25 inches. This stance allows for stability and power during the turning phases. I also set my angles at about 53 degrees on my GS board. I could probably take them down lower, since I am putting them on the Hangl Plate, but feel comfortable, stable and strong at 53 degrees.
For canting I ride as flat as possible. If you have knee issues, you may need to adjust your cants for comfort. I add heel lift on my rear foot, and that's about it. This adds some power, and puts the rear leg in a better riding position for turning.
Good luck. I only put the GS specs here for now, but get GS boards dialed in before you attempt to do anyting on the SL sticks.