The way I do my curb is create a featureline as my eop and use the grading creation tools to create the face and top of curb. This works great because everything is dynamic, so if I need to change the elevation of the pavement the whole curb is adjusted. You could start with the top b/c as the feature line though. Just using 3dpl or featureline and offsetting will not be dynamic so you will have to offset each time you change an elevation.
Steve Goessling
Land Consultants
Civil3D 2015
Windows 7, 64 bit
Intel i7 2600 @ 3.40Ghz
16 GB RAM
Nvidia Quadro 600