Template creation for superelevation

Hi.

I'm unable to find a topic on following issue, which seems to be quite easy, but...I'm designing in OpenRoads and in template there is a simple gravel layer - 20 cm high with rooftop type crosslopes - 4% each. As I create the superelevation, for example, for surface left edge, to elevate and in full superelevation I have onesided crosslope (4%), the left side's subrgade line still is rooftop type - 4% each. How do I make the subgrade line to follow surfaces left edge? I would like it to follow as red line in the sketch.

Thanks.