The balancing folk identified that the spigot on the front flange of the tailshaft and the "cup" in the coupler did not perfectly match. To quote Jeff, "any movement is too much". They changed the flange on the front of the tailshaft then balanced the whole lot together.
(I suspect that the flange was imperial and someone machined the coupler to a metric size believing that the flange was metric.)
The front flange holes now comfortably fit the M10 bolts (butchering gone).
I didn't put it on stands to test it as I had very little time, but I hope to do an axle stand test maybe be next weekend.
My plans is to:
1. Record the vibration audio again just because I am not sure that it's vibrating at tailshaft speed - it feels double that.
2. Try my SS hoseclamp at 45deg increments.
3. Try dampening out the front motor cradle (with my hands) and see how much that is contributing.
I drove to work with about 4.5km of my 15km drive on the tollway this morning at around 90 to 95km/h (traffic speed in left lane) and the Vogue used almost the identical amount of power as when I drive to work via slow backroads. I backed into my parking spot with a reading of 3.14 AH. That's about 125 Wh/km battery to wheel. Wind was practically non-existant - the BOM site also showed almost no doppler wind reading. Current consumption at speed was quite modest. So the Vogue CD isn't awful at all.