A drifter can be longer in the foot if your boat is set up for the increase in foot length. We generally give as much lenght as a cruising spinnaker to allow for more sail area. If you find that your genoa cars are not back far enough, then you can still produce a light air genoa to enhance performance on windless days and still point higher than a cruising spinnaker. Refer to the instructions for measuring for a new genoa or jib.