Bergerie1:
Fifth engine ferry flights are normal on many 4 engine types, and passengers can be carried too. But passengers are never carried when a 4 engine aircraft is flown on 3 engine ferry flight.
Getting more precise with language here: Carrying a spare engine in a fifth (or fourth) pod is not a "ferry" flight at all. It can be a normal revenue flight, albeit with revised performance data due to increased weight and drag.
Engine-out ferry is a different matter. This is done with the sole objective of moving the plane to a facility that can accomplish needed repairs. Takeoff thrust is 75% or 67% of normal. The performance planning must consider the risk of an additional engine failure. Minimum loads; no passengers or baggage. To reiterate, Engine-out ferry is a different matter.