Hubcentric rings only center the wheel on the hub... has nothing to do with stance.
What you need is an 18 - 20mm hubcentric spacer and longer lug studs to reach from the wheel, through the 20mm (or so) spacer and thread into the hub.
38mm offset wheels will stick in toward the center of the car more, rubbing suspension components. Spacing them out 18mm will bring them back to the correct 20mm offset - making them look like the proper wheels.
Some argue that spacers and longer lug studs are not that safe, though - because of extra stress on the longer studs.