This is a very hard technique to perform during a normal play, is near impossible to do what you see in this video when you want... Basically is a little bug.
First of all you have to bring the first boss in a critical damage condition, then suicide yourself to deal more damage to him, bringing the ship at the last damage reachable level.
This way, the bullets pattern become extremely fast, and LONG.
I call this a little bug because the damage level you need to reach is normally impossible to obtain without a suicide.
You can see if the 'Diamond Wave' is going to be activated because after the suicide you'll see the cannon on the 'Ballossum Pench' following your movements; if not, your try becomes a failure.
The final things to do are to try to start the big leech and manage it to the end.

I hope this description was clear enough to explain the mysterius secret beyond this unknown technique.

AST - EXG

P.s.: The video was edited in the beginning of 2006, but i have decided to release it only now.

Final stage score: 5.195.220
Total diamonds amount: 35.857 (less info)