I actually didn't seem to have a problem with this...
Make sure to move both analog sticks in the indicated directions simultaneously - it saves time. Also, ignore the indicator sometimes. If you stop moving the sticks when the indicator tells you, you'll never get to drag it down.
Try to get the SD level. there are two slightly glowing pillars in front of the PC - line the SD's nose up between those, and ensure the thing is level (as if it was flying normally). Then, release the sticks for a moment. If the SD maintains it's level-heading, within a few seconds you'll get the option to pull it down. Do that until you see the approaching TIE fire, then release and destroy them as quickly as possible. Should take between three and five attempts to bring the SD down.
Hope that helps!