I agree with giving experienced crew near total control of the jib. I like to sail by consensus. I started sailing by crewing with a friend who had only a little more experience than me. I experimented with the jib, and soon was in total control with my "little" sail. I was more adventurous and I was the first to suggest we sail wing on wing. Sure its the slowest point of sail, but it was beautiful... oh, boy, that was years ago... Now, we just ask, "Do you want to run jib or main?"

I like to think of the jib as the 'turbocharger', and the mainsail as the 'motor'. Sure, all the power is in the motor, but when you kick in the turbocharger, all hell breaks loose. The jib, instead of forcing fuel/air in to the motor,... it forces more air to flow across the main. More air across the main...more power! When you are sailing up wind, try leaving the mail set to one position, ...then tighten and loosen the jib. You will see the difference. Of course, the situation gets a little more complicated at different points of sail. Get a sailing book from the library, and read about air flow.