Hi Phill,
That pic was taken at our solo champs, hence everyone cat-rigged. At most regattas most of the guys with spinnakers sail 2-up, sometimes the top 2 guys sail solo (when their crew get tired or fed-up), but not often.
At Nationals we haven`t had a cat-rigged boat enter in a few years, all sloop, now with spinnakers. I don`t think a cat-rigged spinnaker boat will be competitive against sloop sailors of equal skill. There are just too many things for one person to do if they are competing against a good sloop crew, who can play downhaul, outhaul, weight position, main traveller & mainsheet, mast rotation on a downwind leg. The top 2 skippers here can get away with sailing solo in a mixed fleet & still do well, but they don`t sail away from the rest of us quite as much as when they have crew. Also, in 15 knots plus the extra weight helps a lot, you can put more power on & hold the boat down.
When sailing solo, you have to decide which of the 2 sails deserves more attention, so the mainsheet & traveller end up cleated while the spinnaker is adjusted, while with 4 hands on the boat, you can constantly trim everything for max. speed.
And as skipper, you don`t have to work so damn hard, man I was finished after that regatta !
In the attached pic I`m about to score one of my 4 "touchdowns". Not good for speed - I capsized twice on one downwind leg, and twice after that, winning the "capsize king" trophy for that regatta.