Seems feasible. Reminds me of the tapered off bike helmets used by word class cyclist. There were wind tunnel tested to finalize the design.
I will try that, but not for aerodynamics though. The design is only effecting the pushing air, the bigger cone is in the front, so the flight should be the same as the standard dart and doesn't affect how the dart cuts through the air.. I could be wrong though.Very cool. My only thought is that as far as aerodynamics go you might want to make the tapered part flush with the cone part. I don't know how much it would affect it, but over longer distances it could slow it down.
It should reduce it, if anything. I will refer you to my thread on cone aerodynamics.My thought being that it could create turbulence..