you can fire as many as you got hooked up... just dont have them touching face by face if you want more than one...
X = Anti Matter Cannon Block
O = Hull Block
XXOXX (This is only 2 cannons, not 4, because theres 2 cannons touching)
XOXOX(This is 3 cannons, because 2 cannons faces are not touching)
XXOXX Is more damage per shot because there is more cannon blocks touching.
XOXOX Is just 1 block for each cannon, good for area of effect damage. not good for peircing hulls and shields.