Dwell times of 6 car 96TS versus 7 car 96TS

I very much doubt that more people will turn up for a train simply because it has 7 cars not 6. The extra capacity surely is for future growth and until that hapens dwell time will be shorter.

From what little I have read in that field, train length is not so much an issue, as long as it is within reasonable parameters (i e, not something ridiculous like a four-car train in the peak on the jubilee).

What matters is flow and throughput, meaning that a large number of doors, with interior and exterior desing facilitating rapid movement of passengers, both deeper into the train, and along the platform, gives generally shorter dwellign times. See, for example, the queing lines painted on platforms in several places around the world, showing passengers where to stand on the platform to end up next to a set of doors, and not stand in the way of disembarkign passengers.

Passengers are a bit like data packets, actually. They don't care how long the cable is or how big the train is, as long as they can quickly get through a door or router.

Ummm. Maybe they don't have enough spare cars?

I believe they cost several pounds each.