[dotancohen]

> Can you show me some references to this?

Lots of people have done the calculations. Poke around the Reddit Spacex forum and NSF forums, lots of discussions there.

> The first goal is to maximize aerodynamic efficiency, which means minimizing frontal surface area.

The fairing is already wider than the first or upper stages, so increasing those stages to the fairing's width would actually improve the aerodynamics.