Aero is important on cars that go fast. My response was to the OP who doesn't have a fast car. His car isn't even built yet and might never be built so my response was aimed at helping him prioritize the build process in an effort to help him actually get something accomplished. Many (maybe most) home built cars never see the light of day much less make WOT trips around a road race course. For a guy working in his garage to succeed he needs to focus on only the highest priority tasks. Aero is way, way down on the list.

Now if the OP gets the car done and starts making laps in the 150 mph range and he comes back here asking for advice I'd then tell him to take a look at some aero tricks.