IIRC that is due to other issues, not aerodynamics.

For instance, the engine no longer receiving oil at negative 1 g, or fuel, as the system is designed for gravity flow.

Stunt planes and airplanes capable of long inverted flight need special oiling and fuel systems to keep the engine from starving from either.

Fascinating! Commercial airliners have also optimized their engines enough they don't have the power budget to make up for the difference in lift.