Thanks for the replies. Got some M6-1.0 bolts, and they fit the tapped
holes on the DW621 perfectly. Fitted some wingnuts onto the bolts.
Was able to find 1/4 inch steel rod. The DW621 has a v-groove bottom , so
the M6 screws force the rod into the v-groove pretty firmly. Steel seems
pretty stiff over 12-18 inch length. A friend helped cut 1/4-20 threads
onto the last 2 inches of one end of each rod. This allows a wood or
aluminum fence to be bolted to the rods. The aluminum is planned to fit into
the slot on one of the popular brands of clampable stright-edge devices,
allowing the router to be completely guided by the slot.