I messed around with some a couple months ago (Mamba with two Large and one Huge OC HY) and it was really nasty against NPCs (but anything is really). Could not comment on PvP. Squaddie of mine is using them for PvP Piracy and seems to enjoy them. Really makes your point when you tell someone to stop then blast the bejesus out of their internals if they don't.
As far as cannons in general they are excellent weapons. Another squaddie has two huge OCs on his Vette and just loves them.
Thanks for the fast reply is good to know that they still have a place under de sun.
To be honest i think cannons are visually the moust badass weapon in the game(especially class 3 and 4) since they are big nasty and scary but like the Unknown Zombie mentioned the grafics and effects left a lot to be desired. Would be nice if the animation was cooler especially when it lands a shot.
i will try using a few OC HYS gimbailed in my type 10 to see if delivers.
That squaddie in the Vette you mentioned is using what experimental effect in the huge OC cannon? auto loader?
regards