As for convergence on the FDL, I use all gimballed guns, could be my lack of pilot skill but even with those guns I often have to move to the left or right slightly to get both sides to fire, especially with the lower medium hard points. Additionally, using the huge requires tipping the nose up some which makes it hard for the top hardpoints to fire... I put the beams on the top since I use them during my warrant scan, then when I melt the shields switch groups to the multicannons on primary and the PA on secondary. Multicannons are on the lower hardpoints so when I tip the nose to fire the PA the distance I need to travel is less.
Not sure if that answers that question, if not let me know.