First reaction: Holy Rumpler, Batman!
Right down to the central driving position and absense of external mirrors.
Second thought: the transition from the top of the windshield to the roof seems too sharp (even Rumpler's car appears to have a more generous curve at that point). The fact that engine cooling is exhausted through the roof is interesting, but even considering that would help to raise pressure behind the transition, it's a little hard to believe the sharp angle wouldn't generate a lot of turbulence. Would be interesting to see a smoke or tuft test to visualize airflow up there.
A similar test would be interesting at the lower part of the windshield to see the effect on flow of those cooling inlets at its base.
Other stuff: nice tight front wheel arch to tire gaps; smooth & flush bodywork from the front to rear wheels is good; the wheels themselves could be cleaner - the diagram appears to show a dish shape. Why not go smooth?