I raced an asymetric Wayfarer World at my club for about 5 years and it was great fun. The spinnaker tends to pull the front of the boat up as well as forward and makes it very stable. When I compared my performance with the asymetric against boats I had sailed against with a conventional spinnaker I found I was loosing out! I also race an RS500 which is designed to sail with the asymetric spinnaker. Modern boats like the RS500 start to plane in a good force 2 and can get the speed on the downwind gybing course that the Wayfarer cann’t. The other problem I noticed was that if you set the spinnaker for a starboard launch you have to recover on starboard as well. Trying to recover on port with the sail being dragged round the forestay did the spinnaker no good at all. Failing to release the wing-wang also resulted in a difficult recovery. I think these problems stem from the length of the foot of the sail which is very long.
ps. I will be at Brancaster on the Wayfarer tidal training event on the 20/21 September. I think I will be in Matt Sharmans boat W773. So if you see me going round in ever decreasing circles, it will be on purpose.