I know Roy's streamliner very well.
When he was coming out with the car in 1996 I done a series of picture, was a very clean work with the frame coating...
The nose shape on the sketch is different to the real car...
To the 6 or 7 degrees - there is a discussion under the aerodynamic specialists for the last 60 years, why there is different - 7 degrees for aeorplane and 6 degrees for ground running verhicles.
To Kamm it had to be around 6 degrees for vehicles - it could be up to 6,2 degrees to Kamm.
I discussed this with the specialist in the Vaihingen University Wind Tunnel - the place where Kamm worked as a Professor for Aerodynamic.
Our opinion was that may be the bouncing airflow along the car makes the different.
A plane, due to this that the air is complete around the plane body, creates a little bit different airflow.
A vehicle on the ground, like a streamliner, got the effect from the bouncing airflow along the streamliner body - this is also the reason for the different effects of flat or round bottom (depense on the distance from the body to the ground).
Rear end 6 inches wide - this is about 15 cm - this has to be enough for a parachute tube - so where is there a problem