Ok i wanted to give credit for the original poster but i will try to redescripe it the way i did it:
1. Make sure to have 2 controllers signed in.
2. Start the game on INSANE.
3. When the game starts, immediately bring the 2 ships to the bottom of the screen. This can be the most tricky part as you are using the 2 controllers.
on the 1st Controller this will attach the first ship to the 2nd one.
5. You will need to quickly click
Twice on the 2nd controller( what you are doing is - Deattahing and reattaching again)
6. By now you will see that both ships are "Hidden" under the black area at the bottom of the screen. You can no longer see them
7. Start shooting with the 1st controller using the
Right Stick to guide missles to enemies on top (they can no longer hit you)
8. You will have to repeat this process
in the start of every level.
9. It can get very tricky in level 3 to do this, because enemies coming at the bottom fast on you, they might kill you before you "disappear", So quickly shoot the bottom line of enemies
and the start the Attach de attach process.