loft between parent and child

hi all,
i want to get a straight, symmetric loft between two relational curves.
first i draw a curve in rhino and mirror it with active history. now i want to use GH to create a straight loft between them, but i cannot select the child curve as input geometry.
same happens, when i mirror the original curve with a GH-mirror-component.
can dependent objects not be used as input-geometry?
can anyone think of a workaround to get a straight, symmetric, developable loft, that can be modified by dragging a single splines´s cvs?
thanks in advance for any help roberto