Bob is probably right about the jib size, but racing 1-up and 2-up competitively against one-another is not as far fetched as it may intuitively.
For a while now the F16's have been doing it quite succesfully. The latter meaning that it is quite hard to predict the outcome of a race when the sailors are of equal skills. It may turn out the Nacra's show a similar phenomenon ?
Just do it and find out !
Wouter