depends on the hood your running. If I put a 600w bulb in a blockbuster it is not centered in the hood, as a 1000w bulb is longer. so adding a socket extension can center the bulb in the hood, giving a more even spread throughout the canopy.Well if u centre the hood that'd make the bulb centered n a 600w will cover a 4x4 so it's alright if it's a bit off
Surly even that said it would only be off by millimetres so no real loss that'd be noticed