What is the aethetic or functional reason for the solid rear wheel rim on the 900 Custom? I love my bike, but if I had one complaint on the visuals of it, it'd be that. Doesn't really bother me to any great degree, but I am a bit puzzled why they went with it in the first place. Does it serve a function, or does it represent an aesthetic that's popular in some quarters (e.g. a design holdover from custom choppers or...?)?