Great work Phil.
The drive train of the M3W is so badly designed and executed.
It's difficult to comprehend how a manufacturer can produce something so poorly engineered, to the extent of ignoring the most basic good engineering practices.
The MMC need to look closely at some of the so-called engineers and designers they employ.
With your own modifications my only concern would be that the fitted polyurethane inserts will reduce the shock absorbing property of the Centa coupling and in time may start to deform.
If they do I'm sure you'll find a solution for that too

I look forward to reading more on your developments.