The 13 psi cap lets the coolant boil at a lower temp and then once the coolant boils the cap releases the pressure and the temp skyrockets. The 16psi cap will raise that point. That's why Nascar uses about 20psi caps.
I understand how it all works, but I also know for fact that a single 16" 2400cfm fan doesn't cut it when it starts getting warm out. (you noticed my location, right?):D
He also said overheating but nothing about loosing coolant.
If he wants to drive that thing and never have to worry about it the full size fan with a full sized shroud is the solution for mechanical cooling.
If he really wants to stay electric then the Ford Contour dual fan with the shroud should do it.
Staying cool on the hiway under load proves the radiator is capable, but a 16 inch circle of airflow isn't.