Disables on a goldfish are rough, especially since it just has the one big gun and two side guns. And with the gun being at the front, sticking as far out as it does, it's gunner candy; just waiting to be taken out. It just takes some fancy flying to try and avoid that as much as possible.
Personally I love the ship, I just think people don't utilize the side guns enough. For instance, if you have a hwacha on the front you can put a flamer or gatling on the side to strip the armor/disable during the reload. Turn back and blam, no more ship. You can do similar with the carronade, using a flamer, missile launcher, mortar, etc. Shooting them as they sink instead of trying to follow them down.
It's a bit harder to get weapon combos flak cannons and lumberjack, due to the angles and range needed for them to be effective. Although the side weapons can always be close range weapons, disables, etc to create an opening to get back at range.
On the other hand, utilizing just the front gun can make an excellent team support ship. Often when I play a carronade fish it's to help keep at least one enemy down and off my enemy. Sink one, then the other, keeping them off my allies back so they can finish them off. Hwacha and lumber fish can be used like that as well, keeping them disabled. While the flak or hwacha fished can be used for rapid kills once your ally takes out their armor.