Here is a link to a thesis published by a Naval Officer who used CFD study to determine an optimum aerodynamic shape for an aerocap. I had posted this link some time ago here on ecomodder and many found it informative.
It is interesting to read what this report says about a conventional camper shell. It is also interesting what fuel efficiency percentages were realized by the author, who built his own aerocap for this study.
Hope you find the report informative.
Bondo
http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf