The rules also state that if you sail single handed you go without a jib, and double handed you go full suit.
The latter part is not true. You are always allowed to sail with fewer sails then that allowed for your setup. In fact this means that a Uni-rigged F16 may be sailed by 2 persons. And indeed they will only be slower for it, so what is the harm to others ? Same for sailing without a spi.
Wouter
