Hey Ant,
Well, it has to do with roll resistance. My swaybar mounts to the axle pretty far out on the tubes. So, the swaybar has to move much more than if it the links were mounted closer to centerline.
The 1-1/16" bar simply would only move enough for 8-10" of articulation, it was too stiff. That was the max movement it saw, it would lift the drooping tire before allowing any more articulation. By reducing to a 7/8" bar, it will move enough to give me around 16-18" of articulation. Since your running a bar about the same length as me, they are decent figures to go by.
All their swaybars use a 1", 48" spline on the ends, that way they have universal arms. They use 1.75" OD tubing, but I forget the wall thickness. You slide the bushings in the end of the tubes, then slide the swaybar through the bushings and attach thte arms.
CJ