Hi, I can't find the brainmask of the T1 mayo atlas after downloading. It will be really great to have it. Any help would be appreciated.

The tissue probability masks can be used for this. You can take MCSA202_tpm.nii and sum+threshold the first 2 (GM, WM) or 3 (GM, WM, CSF) channels to arrive at whichever notion of brainmask is needed.

However, including these directly is a reasonable request, and we will plan to add them in the next release.
Thank you for providing your feedback!