For wider legs, I usually still put an inch of 1/1 ribbing at the top, with lycra or elastic for grippability, at a fairly loose tension (looser than normal), and then go to 3/1 ribber with even looser tension. This gives a sock that stretches to a fairly wide diameter.
On the opposite end, when I'm trying to fit a narrow foot, I might use 2/1 ribbing on the leg (54/36) and then use 2/1 _mock_ ribbing on the foot -- the lack of stitch for the mock rib draws in a little more than if the purl stitch was present. That worked out really well!
(posted by me to sockmachinefriends this day)