That may have happened to me once or twice, but I usually found the bombers to be more of a threat than the Nero. At any rate, the best advice I could give you is to try to stick close to the Sai and to order your wingmates to protect it. If you find that the Nero consistently fires on the Sai, either take out whichever beams are firing at it yourself, or else order your wingmates to do it. Without spoiling anything, the Nero won't have a lot of time to do damage to the Sai, so you'll only have to keep it busy for a little while.

Oh, and before I forget:

Exits are to the front and rear. In case of an emergency, you can and will be used as a flotation device. There are napalm throwers under the seats, but they're full of water; you'll have to use them as bludgeons. Plasma rifles are available in the weapons lockers, which can only be opened by an admin, God,

, or hyperintelligent shade of the color blue. If you find yourself crawling through the ventilation shafts and come across a Shivan, don't worry, it's only Carl. Just give him your lunch, and he should leave you alone. Enjoy your stay!
(Apologies to any veterans if I screwed it up; this is the first time I've had the honor of delivering the welcome speech.

)