I know this is a strange one but got to ask the question..

Any one familiar with bike racks for the Z4? I am a recent owner of a Z4 and my other hobby is cycling. I am looking for a way to carry my bike on the back without using a trunk mounted rack. I have spoke with a custom trailer hitch place in town and they are recommending a "vertical" receiver tube mounted behind the bumper that is virtually invisible when the rack is not installed. The rack will have to be customized to work with the vertical hitch instead of the horizontal tube. The company stated they have done these types of hitches on Audis and Porsches. I have seen the verticle tubes on motorcycles but not on a car. It seems like a good ideal. Anyone have any experience with this type of hitch on a Z4?