GaijinPunch recently asked the same question in the high score thread. My reply was as follows:
I suggest double missiles, though it may be possible without, especially if you're better at small taps of the joystick than I am.
Before the pod begins moving, you'll want to position the Opa-Opa in the upper right corner, facing left. It's been a while since I've played, so if the far right corner causes the pod to turn
right, move this starting position a bit to the left.
Once the pod gives chase, you will want to slalom in a very deliberate manner: track left as little as you need to be safe, then move to the very bottom of the screen. Track left as little as possible, then move to the very top of the screen. Repeat. In the short sections where you track left, you want to make sure the pod has gone as far vertically as possible. You might have to pause a beat before continuing to make this happen.
While following that pattern, your weapon of choice is missiles. Only fire the missiles when both you and the pod are moving vertically. The missiles you fire should travel straight up or down and the pod should ram directly into them. If performed well with double missiles, the pod should die before you reach your last two columns of space.
Graphical representation of route. Hatchmarks are where I recall launching missiles. If it's possible to fire two volleys per column, do so!
Good luck!