A partition with a deflection head must not have services penetrating  in the deflection zone.  All service penetrations must be run below the flat strap, otherwise they will interfere with the movement of the detail.

The distance between the soffit and the permitted service installation zone will vary depending on the deflection allowance. It will be the depth of the fire board packers + the depth of the head track (determined by deflection table) + deflection allowance (this is left between the track and the flat strap to allow the stud to deflect) + flat strap width.

Based on a common 25mm deflection for a single layer board system, a penetration free zone of 195mm from the soffit would be required.

For a 45mm deflection head, a penetration free zone of 255mm will be required.