A lj/flak Galleon and a lumberfish are two extremely different things.
One is a stationary fortress that wants to deal as much dmg as possible and the other is a support disable ship that wants to set up good engages for his ally.
You cant compare those two just cause both use a lumberjack.
If i imagine a lj/flak galli instead of the lumberfishes in the competetive matches i probably get to the conclusion that the galli wouldnt work in that situation.
As I said, the effectiveness of the ship is entirely dependant on the gunner's skill with the weapon, you can still achieve the same results with all 3 heavy gun bearing ships, the gun has the same purpose on all of them and that's to disable an enemy, except on a Goldfish, if you lose said gun, you lose all your firepower at range and since you need to stay still to aim an LJ, you are an easy target that will have nothing esle to fire if you lose it.
That's why I personaly think that it's less effective than say a Spire doing the same thing, even a Galleon, it doesn't matter. It's your opinion and this is mine, now can we stop derailing?