I was sorting through my collection of research papers, and I happened upon an interesting one published in the AIAA Journal of Aircraft,
Wortman, A., "Reduction of fuselage form drag by vortex flows," Journal of Aircraft,1999, vol. 36, no3, pp. 501-506.
The idea has also been patented, which provides details of the device,
The basic idea is to place large vortex generators at the beginning of the tapered upsweep of the aft fuselage in order to reduce the magnitude of flow separation and hence drag. This area of the fuselage has always struck me as one that would act like a bluff body and contribute significantly to the overall drag of the fuselage.
I'm curious as to why this idea has gained so little traction? The author claims a drag reduction of up to 1% for a 747, and 2% for a C5 Galaxy. These certainly seem to be worthwhile gains given the relative simplicity in implementing the idea in practice.