As has been discussed a few months ago, out of every rating category ‘Balance’ is not very clear at all. It has no explanation nor discernible meaning. As such, i suggest replacing it with a category that is more important: Gun Handling.
What is Gun Handling? The practical difference between the Archer and the Achilles, or the Harry Hopkins and the Crusader II. They effectively have the same guns, but one is significantly more effective. In this way, while ‘Firepower’ would be primarily about the effects of the gun on target, ‘Gun Handling’ is how well the gun gets on target in the first place.
In this way, the effect of stabilizers or bad depression angles can be better ascertained, without downplaying the role of the cannon itself.
Edit: Besides, a little hover over explanation on all the different ratings would be handy too.