Recently I mounted the rain guard from Zero:
https://www.youtube.com/channel/UCLZ..._bq2tSdJ_a-0eg
And I'm pondering about what it does from an aerodynamic standpoint. On the on hand it adds a bit of drag due to extra frontal area, on the other hand most of it is behind the riders legs anyway and it could combat vortexes that come from the rear wheel?