I finally found some time to work on the model again and so I added the torpedo tubes at the front. I have set a torpedo to a length of about 4.5m and 0.2m radius. Taking that size I could place 8 tubes at each side which makes 16 tubes in the front arc. The rest of the 40 tubes will be placed along the sides of the ship about the placement as in the movie.
The lauchers are normaly protected by blast doors. The pic shows the "open fire" position. Right in front of the torpedos is a little window, airlock and some maintance doors for quicker access to the tubes and thrusters if repairs are needed.