Solution : Go through 2-1 on Order Field, try to destroy as many of the white turrets as you can to have a maxed MetaStock when the boss goes down. If you have less than ten MetaStock units filled, this won´t work!
At the beginning of 2-2, switch to Chaos Field. Keep comboing and damageing the boss (Preferably while using well-timed wing-layer attacks instead of lock-ons) until it starts to prepare for its brief departure. Immediately cease all action and try to catch some of those green bullets that the middle section fires in a huge spread with a lock-on. (You might need to practise your timing with this; if it seems impossible to do, a wing-layer attack and some fancy maneuvering will also do a fine job... may be even an easier one.)
Now hold your breath : Normally, even if you´d manage to lock on a bullet at the very moment the boss leaves to the right, your combo meter would be drained before he re-enters.
But here´s the trick : Everytime you use the Lock-On Attack, the combo meter stops for a split second, even if you don´t actually lock onto anything! And that´s what you got to do, just use some lock-ons when your meter is halfway drained, and you will get that nick of time you need to lock onto the boss when he has re-entered, so you can continue chaining!
It would be wise to switch back to Order Field for the rest of 2-2, in case you might be short on MetaStock. I also advise you to slash away at those blue cannons on the boss' "head", they give a good number of MetaItems and don´t have as much health as the large cannons on its side... You have to re-stock pretty fast, or all your effort will have been wasted.
As soon as the artillery goes up in blazes, you can pat yourself on your shoulder, you´ve done it!
Please note that this was achieved while playing the GC version´s Arcade Mode using the Flawed Red ship; it may not necessarily apply to the DC version or the Mixed Blue/Fake Yellow ships (because their lock-on may work different regarding that matter). I´d like someone who plays the DC version to confirm this; thanks in advance.
