Grade Labels: Make L1% = CL% = R1% ?
Question
"...I’m looking for a setting so that all the grades along a curve in road (namely, left and right curb) will match the grade at the centerline..."
Answer
The answer to that question depends entirely on how you're creating the grade labels. The two available methods are "Flow Labels" & "Plan Labels".
Flow Labels: Not possible
Uses Design Marker elevations
Cannot detect paving features, paving data nor Base Map Control
Uses direct data measurements for calculations
Can only display true-grade values
Plan Labels: Configurable
Uses Paving Data elevations
Uses Base Map Control (label orientation, length calculations)
Can only display true-grade values with True-Length Paving Features
Bottom Line
You can do this, but you've got to suppress definition of TL features, otherwise the labeling algorithms will detect them and use them to calculate the true-grade.
So if the following are all true, offset grades will match centerline grades:
Stations match on each component
Cross-slopes match at the starting and ending station of the labeled length of pavement/curb/gutter
No true-length paving features are defined along the labeled path