What I do:
Start right away by pressing C-3-8 and then C-5.
Max power to engines and full burn to the beams.
Fire 1 Treb each at 2 fighters, chances are you'll take them down.
Lock onto the beam, make sure that you have dual fire on, and fire the Helioses when you are less than 300 metres away.
Repeat with Beam 2.
Let the Support Ship catch you, and once you're reloaded, take out the other two in the same manner. Use dual Trebs if the beam only has a small amount of health left after being hit.
Reload, and take on the Beleth. Make sure to disable it first.
Wait for 30 seconds after you destroy Gemini, because a new wave jumps in, usually as you are jumping out.
Make sure to press C-3-9 after the Sath leaves.