because the spinnaker on the I-17 comes out of a bag, it doesn't have to be cut very flat

it will have much more curvature and so always be able to sail deeper than a roller furling sail

you just don't have the right sail to sail as deep as the other boat

however in light winds and highish angles you should be able to outsail the I-17 on tight reaches

the last tornado sailing olympics had this contrast when the usa team, expecting very light winds, used a very flat reacher hoping to outpace the other boats with deeper cut spins

in the event the wind blew hard and the usa team could not compete downwind with any of the other teams and ended up doing very poorly