"Perhaps there was something in Jimmy's idea all along as can be seen by the approach of experienced designers such as Russell Kauffman (of Russell K loudspeakers) who don't use any wadding/damping material in their current designs. Instead they seek to work with resonances instead of against them."
Can you see the logical fallacy in that statement? Damping materials also seek to work with resonance. There is no getting away from resonance, so any and everything you do to a cabinet can either broaden a resonant peak or attempt to reduce the peak resonance in magnitude or you name it. But resonance is there, regardless of how you treat it, so not treating it is just another choice off the "treatment" menu.