The air behind the cockpit and around Halo is quite bad, it's almost as bad for radiator cooling as the front tyre wake. I don't think those openings above cockpit are used for radiator cooling, but rather for some internal flow conditioning, most likely complementary along with (internal?) S duct outlet. In theory, you can get away with smaller radiator inlets if you manage to increase the pressure difference between inlets and outlets and internal flow management is crucial for that. Introducing a bit more cool air also helps
