hmm, for the sail sizes the 78 sounds better and the spots. But the width on the Mamba is obviously narrower due to the straighter outline - so when no wind, can be a bit more challenging than the Grip 82 which is obviously bigger and wider. But a 3.4 on the Mamba 84 is also too big for her weight. On the other hand, she is light and mainly in stronger winds, so I guess 78 is the better overall choice, has plenty of planing power. Second option Grip 75, also for you then when it gets really windy? :-)