Typically there are no limitations on armament in 1:144 Big Gun, other than it has to be 3" or higher. WWCC was the sole exception for a while, but rescinded it recently. The Big Gun saying typically goes: if it is over 3" and you are skilled/crazy enough to arm it, go right ahead! The corollary is don't be surprised if stuff breaks more often due to added complexities. Most folks just arm the primary battery and leave the secondary and tertiary batteries alone.
Jeff Burns
BGCWI