Collar-Less Routing for Contours
My mission was to advance a V-Groove accent parallel to an arc contour on a header piece. One approach would be a fab up a companion jig with the same contour, attach it to the header piece and use a collar to follow the contour throughout the arc.
Another approach would be to fab up a simple jig that attaches to the base of the router possessing two skate board bearings attached with a two 5/16" T-Bolts. The two skate board bearings ride along the vertical surface of the header allowing the advancement of a V-Groove 1-1/4" perfectly parallel to the header contour. This jig works for any path shape you want the skate board bearings to follow; beit straight, curved, arched, splined, circular, etc. Care must be taken to keep the bearings firmly against riding surface and, viola', your router bit will dutifully follow.