As far as I know, the shark's fin for both E60 and E65 models are only used for the purposes of the GPS Nav and Carphone, ie. basically the communications, functions. The tuner and remote controls antennae are housed in the rear windscreen. So, I am not sure if the sharksfin would serve your purpose.
The tuner reception for my previosu E46 was also not great. However, I think that is is likely to be due to the limitations of the tuner itself rather then the position or type of antenna.
The tuner reception for my previosu E46 was also not great. However, I think that is is likely to be due to the limitations of the tuner itself rather then the position or type of antenna.