To improve the splitter's efficiency, there are twin diffusers and vertical vortex generators in the area of the splitter that feeds the lower pressure wheelwell area. The vertical vortex generators or strakes enhance the action of the diffuser area
The diffuser takes up every bit of the available area under the splitter/belly pan. Note the elaborate vortex generator assembly at the end of the splitter. This generates strong tip votexes that help reduce the amount of air curling underneath the car from the sides which improves the effectiveness of the rear diffuser. It also helps improve the stagnation of the splitter on the sides of the car where due to the pointed nose, it is hard to build a pressure differential.
The splitter/belly pan is very solidly attached to the chassis, important because it can generate several hundred pounds of downforce. As the car is developed, effective ducting will be built for the heat exchangers in the car's nose which will improve aero greatly.
The sides of the car feature barge boards and fences. The barge boards increase downforce in much the same way that a splitter does and the vertical fences aid in pressure recovery by trapping the air and keeping it from curling under the car. You can see in this photo how the front vortex generator is perfectly placed to assist the side aero function. You can also see how all air from the wheelwell is vented and fed to the barge board area for drag reduction and pressure recovery.
Here is another view where you can see the elaborate vertical fences on the barge boards. The way air is managed from the wheel well with tall dual curved fences is fascinating.
A closer view of how wheel well air is managed. The barge board has an extensive leading edge so the air from the spinning wheel is utilized. We have hardly ever seen such well though out aero on a works car much less a car from an independent shop.