Thanks Francois.
Briefly, the problem we are having is this.
We are using Desikan with 68 regions but we only have 62 electrodes.
This means after source-localization some of the 68 are not independent time series.
In order to perform leakage-correction (orthogonalization, all at once, not pairwise), we need to have 68 independent time series.
Hence, we presumed we needed to use an atlas with fewer regions.
The Schaefer seems to have many regions.
The Yeo 17 has 17 networks. This means (i think) that network 1, for example, will have multiple regions spread across the cortex but only provide a single time series for that network.
This is not quite optimal for our purposes.
For the above reasons, I have imported a version of the Yeo with 29 regions per hemisphere (composed of the 7 networks).
You can see the 29 individual regions in the picture above.
I trust this comports with your own understanding?
I was just a bit concerned that the downsampled atlas has somewhat of a patchy appearance.
But maybe this is normal?
Apologies for the long explanation.