It's been a year or more since I formed the view that cantilevers might well flex. At the time, I constructed a theoretical model of the cantilever as an underdamped transmission line. i.e. as the stylus moves, a transverse vibration propagates along the cantilever, rather than the whole cantilever moving as a body.
At the time I posted this plot, which is a calculation of mechanical impedance as seen by the stylus moving a cantilever of typical construction which is pivoted at one end. With zero damping, because maths was too hard to incorporate, so I sketched on the effect of damping as a dotted line :
Now, this could be rubbish. I didn't progress it because it seemed to imply that cantilever flex defined mechanical impedance, rather than the elastomer. Which seems implausible. But, if one believes cantilevers can flex enough to be self resonant, there should be an impedance dip at the quadrature frequency (resf/4).
Were this true, cantilever flex would be providing a significant part of cartridge suspension spring, i think. This is the sort of iconoclastic thing that is awkward to ignore if one accepts the top resonance is due to cantilever flex though.
But, I could well be wrong. Or I may be right, it does fit the profile. I think it needs an independant confirmation.