ORIGINAL: robert
I think I see what you're saying. Having the fins away from the aerodynamic centre isn't necessarilly a bad thing. Just think of the stab or fin, the moment they produce is used to counter other moments and add stability. But these fins are designed to add lift in knife-edge, not for stability. By having them on the CoG they won't change the attitude (yaw) of the aircraft at different fin angles of attack (sideslip angles). All they do is add lift.
Yes!!!!!
ORIGINAL: robert
By having them say behind the CoG, you're actually adding in a sense to the size of the fin at the rear of the aircraft as it's adding stability as well as side area. In fact, if you were to put these fins far behind the CoG, so that the moment they produce during a side slip is large, you would have to increase the size of the rudder or it's throw. This is because the rudder will have to 'fight' the extra stability provided by the fins, which may be counter-productive for pattern.
By having them say behind the CoG, you're actually adding in a sense to the size of the fin at the rear of the aircraft as it's adding stability.
But it's not necessarily an advantege... may be for one flight condition; but could be even dangerous for others...