Thanks to my good friend, Erik, I got one .... A perfect fit with the AFS 105/1.4 E. Plus probably a lot of other Nikkors.
The added extension brings the magnification of the 105E into a highly useful range, as witnessed by the (admittedly boring) shot of a Campanula latifolia flower on the recent Norwegian trip with Erik. Here I have stopped down a bit, to f/4.5, as the subject itself is 3-D, yet the bokeh of the rather busy background remains commendably smooth. Detail sharpness is up there with the best "macro" lenses.
Only the vestiges of axial colour hint that a non-specialist optic has been deployed. As always, don't think the master lens won't suffer from added extension if such isn't a planned part of the optical design. The claim that extension adds "no glass" is trivially true,; however, the extension in itself alters the conjugate distances and throws them outside the designed range. Since the 105E starts out being such an exceptional lens, it fares pretty well with only small signs of increased field curvature and increased chromatic aberrations.