(There are only observations & questions here. Perhaps someone out there has an answer)

Although the universe appears to behave exponentially at large distances, for red shifts below 0.2 we can assume a linear relationship. I took a wavelength the size of the observable universe and began to halve this down on a spread sheet, as one would do with a sound wave to get the next octave. To save you time on this, if you take the size of the observable universe and divide by 64 twice, then you have the length of one mega parsec. This is a bizarre coincidence. This length is important because it also coincides with one of the apparently preferred red shifts of around 73 km/s as do integral multiples of this value. There are also sub-multiples of this value eg half, third, sixth where quantisation has been observed.

It is reasonable to assume that these are not really positional shells of galaxies like onion rings since this would put ourselves as being the centre of the universe. An alternative is, that it must be some sort of illusion which is distance dependent. It is just as if em radiation had a longitudinal component. Waves through the earth or water can be both transverse and longitudinal. We know that the em wave has a B and E transverse components. Could it possibly have a longitudinal component as the waves interact with the virtual positron electron pairs and give up their energy to the background?

The reason for this speculation is that the quantised/preferred red shifts appear to coincide with the nodes of standing waves and submultiples thereof based on the fundamental wavelength of the observable universe. Take one mega parsec and fit different 'harmonics' of standing waves inside it and the nodes correspond to the observed quantisations. Furthermore, where a number of nodes from different harmonics coincide the effect is reinforced. The mega parsec is already an 'overtone' of the fundamental wavelength as can be seen from the above.

In terms of red shift, then one mega parsec at 73km/s has a red shift of 73,000/c = 0.00024.

Other apparent quantisations appear to be based on combinations of multiples and submultiples of this value. i.e. the nodes of enormous standing waves.