You can also use a longer bolt and attach the rack to the seatpost clamp.
Used this method on a M2 Stumpjumper that only had the dropout mount points.
Only difference was that had a removable seat clamp, but worked fine and in fact someone actually made a clamp with rack bosses built on it
Used this method on a M2 Stumpjumper that only had the dropout mount points.
Only difference was that had a removable seat clamp, but worked fine and in fact someone actually made a clamp with rack bosses built on it