Depending on which Contessas you have, you may not need stepped drums. There's two different offsets.
The common type was intended for Minis with normal drums and fits without any flares required. If you fit this type with stepped drums the wheels stick out and flares are required. My van (on my website) has stepped drums and this type of Contessa. I swet my van up this way because I like the look with the flares filled out.
The other, less common type was fitted to Mini LS 998 with factory stepped drums. They will fit on a car with stepped drums without flares required but will foul the rear trailing arm on a Mini with normal drums.
Hope this helps!