Stair stringer offset

[jledgewood]

I would like to change the stringer to a wide flange and be able to have those wide flanges offset to the underside of the stair treads and risers. when I have stringer selected I can change the type that it is but not where it sits relative to the stair (unless I am missing something). when I change from stringer to carriage I am able to choose an offset but not able to change the type to another shape i.e. wide flange.