Something on the TAU Ion Cannon always seemed wrong to me and the new codex made me take a closer look and do something about it.
I am a frequent visitor of advancedtautactica.com because the knowledge on TAU is nowhere as big as there. Ans somewhere there I stumbled about a picture of a guy who extended the overall length of the cannon so make it look more feasable.

I couldn't remeber the name of the guy (or gal) but I remembered the changes quite well so I took the chance to do something similar for my hammmerhead tank. I made a copy of the barrel with instamould and magicsculp, added some tubing and thats really it. You can see it after assembly and after applying camo by use of airbrush.
Ion Cannon with longer barrel

Ion Cannon with longer barrel

Ion Cannon with longer barrel

Ion Cannon with longer barrel