But a Cd of 0.11 is only "quite good" for velomobiles even at the time my GoOne had been built. Check for example the specs of the Milans:
Milan Velomobil - Die Zukunft der Mobilität (Cw = Cd)
The latest successor of my vehicle also plays in that leage.
But anyway i think i should work from front to back in order to improve the situation. And i am looking for partial results: entirely closing the back is not possible due to the stability problem of my back wheel, which can only gradually improved, and it will destroy the design idea.
Anyway - there are some recent attempts:
a) successful
b) mostly unsuccessful
(i had closed the gaps with tape before driving)
Here an early version - i had to shorten the back because of the strong sideward moves of the wheel. The other GoOne is younger and had been improved by the manufacturer.