You can find Class 3 Gimballed Cannons at Beta-1 Tucanae (Adams Orbital) its what I am using on my Python. I was using 3x Large Gimballed Cannons and 2x Med Gimballed Beams for melting smaller ships. I am however thinking that I am going to move to 3x Large Gimballed Pulse and 2x Med Gimballed Multi-Cannons. I have not played this load out yet so if there are heating or other issues I am open to inputs. My current load out is great for larger ships and Anacondas - but with the current swarming of smaller ships in the Combat Zones I need to rethink my build a bit.
That post was from January. At that time, Class 3 Gimbal Cannon did not exist.