depends on the situation.
Are you using the cage as a shield? e.g., can you tighten the gap between the cage ahead before that green-light intersection where the zombie in the minivan wants to take a left into your right-of-way?
In that case I will hang to the left-of-center so that I can see the zombie and then drift right and use the cage as a shield while simultaneously giving myself a bit of room to squirt away if necessary. Perhaps my drift will also alert the cager I'm following that I am in fact following him (he'll see my headlight drift across his rearview). I'll keep an eye on both cagers as much as necessary.
Another case: Entering a blind right-hander. I keep to the right of center and allow the cage ahead to absorb the impact of any zombies that are drifting over the lane marker. If you're to the right-of-center it's a bit more likely that your view of the road ahead (as seen thought the cage in front of you) won't be blocked by the A-pillar of the cage, as it might be if you remain left-of-center through the turn.
Don't forget what Animal Mother said in the movie 'Full Metal Jacket':
Better you than me.
The whole lane is yours, as is the zombie ahead of you. Use both in good health and good forturne.