The SPAdd3PtArcLabel allows the user to place Curve labels along arcs by picking the Start point, point on arc, and End point.
Type SPAdd3PtArcLabel at the command line or select it from the Sincpac2 Ribbon Tab, Tools Panel, AddLabels drop down. You will be prompted to pick the 3 points defining the arc to label. This tool uses the Drawing's settings for General Segment Label Layer and Styles.
Add labels and drag as needed with the styles swapping based on location of the drag point.