Most elegant solution to add rear brake cabling to a track frame?

stick these under the top tube, don't bother with having no outer cable in the middle because if it means that you got to have huge silver clamps around the top tube, it would be pretty conspicuous and ugly.

They are made by BBB and are smaller than they look in the picture.

these look good, but my frame is all chrome, so a black patch might be more visible than a silver ring (if it's thin, like in the first image)