I've used rudders well in pairs, one at the front and one at the back. Just do some testing with them, in the testing range or a private server. Fiddle with the different left/right options and the front/back placement. You've basically got 4 options, front/back/left/right, just change them around and see how it handles.
Aye, I use ships with rudders like this:
One rudder in front (Edit: or in this case, two in front, JUST IN CASE), one in back, directions on them reversed from each other, both set to 45. The further they are from the center of the ship, the stronger they will affect the ship.
The front fin makes the ship turn faster, the rear fins combined with the front one make it more stable (it stops turning instead of continuing forever).
The only problem with rudders is that unless you also include expensive maneuvering thrusters, you can't turn or strafe while stationary.
It's also worth noting that a rudder is just a fin on a turret. If you need some POWERFUL rudders, then set a turret and then set a large fin on it. If you follow that concept, then a fin's purpose is to turn angular motion into forward motion - that is, if you take a turn and your ship slides, the fin is there to give you "traction" in the air and prevent sliding, ensuring that your direction of movement is the same as your direction of thrust. Or rather, the direction of movement wants to be the same as the direction of the fins. That's the real thing about fins and rudders. All they do is try to face you in their direction, more or less.
Hmm, it might then be possible to combine the fins and rudders. Of course, uncombined it's less likely to break down entirely from battle damage.