Thanks JSF1,
So A321 Green-Dot speed calculation is different from the A320 one that I posted above. Instead, it is:
[GW (in tonnes) X 1.5] + 110
Do you still have to add 1 knot for every 1000ft you are in excess of FL200?
The 1.5 factor means that, referring to my above post, a Green-Dot discrepancy of 10 kts would imply a GW discrepancy of 6.7 tonnes on the A321; and a 2-tonne GW-discrepancy would produce a Green-Dot discrepancy of only 3kts.