Well, being at convergence distance is ideal for most killing power with 0.50cal MGs. Either at exact convergence or +/- 50m within the convergence distance.
When you got 200m convergence, and your shooting at enemy from 500m distance, taking 1 sec snapshots at 90deg deflection bandits, don't expect the enemy to explode!
On the other hand, 0.50cal tends to kill and wound enemy pilots eventually. High rate of fire tends to help in this also, in my opinion.
Even fw-190 burns up nicely, when you hit his main fuel tank, behind pilot seat, a couple of times
I think aiming along the centre fuselage is good with these 0.50cals (unless you're against Japanese planes, wingroot is excellent target for those)
If, you hit the engine, or pilot, enemy is going down soon. Center fuselage hit can probably light up main fuel tank, or kill cables. Rear fuselage would destroy elevator and rudder tabs, and cut cables.