The full-race version of the 911 GT moved the mirrors way ahead of the A-pillars to get them into slower air,and they encased them in long,higher fineness ratio housings,kinda like Mair's wind tunnel model.These mirrors might have something on the order of Cd 0.20,excluding the mounting struts.
http://www.porsche-mania.com/wp-cont...he-911-GT1.jpg
Here is Mair's 'template' with the cylindrical elongation removed
