That subassembly is not going to allow you to do the design the way you want, and, as far as I know, none of the other stock subassemblies allows benching.
You might consider posting to the Civil 3D customization group and asking if anyone has modified that subassembly to allow cut bench slope and fill bench slope, or you might be able to contract someone from there to write it for you.
Tim Corey
Delta Engineering Systems
Redding, CA
Tim Corey
MicroCAD Training and Consulting, Inc.
Redding, CA
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