Honda R&D investigated the catamaran body with their Dream solar car series.I don't have the source with me,but my failing memory tells me that their 1996 Japanese Society of Automotive Engineers paper claimed that the catamaran generated about 20% higher drag than the 'pumpkin seed'/'flattened-torpedo' body.
Here is one of the bodies they chose for competition,which won the World Solar Challenge.It has Cd 0.10.
