the original model, the Akatonbo Rin Kagamine model was compared to the Aratana Len model.
There are a few differences, in that the groove bone is after the center bone, and not before. This differs from the steps above. But i have identified how to make it work.
The model needs the following, in this order
Parent master bone (0,0,0)
Center (0,8,0)
Groove (0,7,0) - previous center bone
Use the 'add master bone' function to start off.
Rightclick the add master bone, and add a connect bone (Ctrl+L)
change its name to a center bone (change the coordinates to 0,8,0)
change the old center bone to groove bone
change the coordinates to 0,7,0
ensure that all the bones are connected in that order.