No you are incorrect ,the Octura ZX has only bow plains and its 4 batteries are spread out in the hull or the weight is spread out ,also in water a sub can have a very forward cg or forward bateries and as long as its counter ballanced with foam the cg can be shifted but only in water can this happen.Once in motion the cg changes again in turns and dives.
The Graupner Shark that I own has only forward plains and manuevers like a dream got to get ya one!
Think of it this way why are torpedoes made with aft only control serfaces?They are that way so that with little or minimal movement on a already constrained machine since it comes out of a tube , that it will hold true to its course,it does not have to make very sharp turns to hit the target,if it did have to make  sharp turns I would thimk that forward plains would be added.

A good case in point would be my SB-2 it came with tiny forward plains that for the size of the sub where vertauly useless,it was not until I made them six times larger that she finaly manuevered incredibly better,just like a fish from a slug to a shark!
Also the added benifit of having operational bow plains is the preciese depth control while at pariscope depth ,vital on Military subs,I have not seen very many without them.

As the sub dives the forward plains move first as seen in many movies prove, they are moved making the sub  attain the correct angle not too much and too little,if they only had aft plains the sub would not be nearly as controlable as trim tanks would have to be used and would take much longer to control the dive angle,in war thats not good!

In my experiances the sub with the most effective forward plains out manuevers by far a sub that has none or ther just too small along with stern plains.

The Typhoon has also very effective aft plains being that there right aft of the Kurt Knozzles that is the best way for aft plains any thrust is imidiatly used to deflect the thrust current and effect a change in attitude however look at those huge forward plains there that way becuse the sub is so huge and wide that aft plains alone are not enough.


Dave