From what I know, a center post build is when you center the
coils as to improve airflow and have equal wicking on each side.
Since I've started doing them, I haven't really noticed a significant increase/decrease in performance. I guess I could say that my smaller ID
coils wick better during chain vapes but that's really it.
The way I make mine, I make two normal coils and leave longer legs, then while still on the drill bits, I'll use a flat head screwdriver to push on the center leg and make almost a crease in it, then push the other side in. After they're pretty centered, I'll glow and pinch them in to shape.