"Very Heavy" According to the FIRE article, I would assume this implies ADR5/SDR1? Go, plasmic tungsten fireballs.
What's the shredder's hull look like... SP5 Hull/SP5 Shields? Oh gods, this is going to be a loooong fight... at least until the Acadia and Emden arrive on-scene anyways. Let's see, that's ten shots per gunboat minimum... I've got 80 shots myself, anyone with a single PAL has 40...
We should be fine as far as taking them down is concerned, surviving is another matter entirely.
And Fian, rate of fire on the PAL states rate of fire at 120RPM (1 shot per five seconds), I assume this might degrade when mounted on the Aggressor, but that should still give us about one shot per case per round (assuming an abstraction of about 10 seconds per round). Which implies, as my number-loving brain is wont to do, that combat is taking place at a rate of 5 seconds per cycle.