We also sail in a mixed handicap fleet (mostly against RS200s) and one of our members have a W World that used to race with an asymmetric rig. They soon changed this to a normal symmetric spinnaker as they found that it was faster. Wayfarers are really too heavy to gain any particular speed advantage from reaching with a gennaker, rather than in a straight line down wind. We race on a level handicap with the RS200 and it rather depends on the course for us to beat them. Straight runs against the tide= we win; reaches with the tide = they win.