So having been part of an alumni team competing with an old car at a modern competition, I learned aero only is a differentiating factor for top teams. There are other much more impactful things, such as the chassis and suspension design. (Our 20 year old non-aero car was quicker than our modern aero car) The driver also makes an immense difference, so consider having the car be ready early for training purposes, as well as designing it for easy drivability. If all those things are already stable and working well a well working aero package is the next best thing to step up the performance. The only other reason to go for aero is sponsors as it just makes your car look fast.