Hello Pete,
Thank you again for your help; I am following your suggestions and they are helpful.

I wanted to ask you one thing regarding the Haskins atlas. In the first-pass, I performed group analysis on sample ages 8 to 21 all having non-linear registrations to the TT-N27 template.
There after, I identified significant clusters with 3dclust (placed in clust+tlrc). Then I ran whereami of these clusters using both CA_N27_ML and the Haskins_Pediatric_Nonlinear_1.0 atlases, that is,

whereami -atlas CA_N27_ML -omask clust+tlrc

3drefit -space HaskinsPeds clust+tlrc;  
whereami -atlas Haskins_Pediatric_Nonlinear_1.0 -omask clust+tlrc

The idea here is, for the first-pass analysis, I would report ROIs overlapping with significant clusters under both the CA_N27_ML and Haskins_Pediatric_Nonlinear_1.0 atlases (separately).

For example, it could be somehting like:
CA_N27_M: Left Insula (73.9%), Left pars triangularis (9.9%)
Haskins Pediatrics: Left pars opercularis (53.6%), Left Insula (26.2%), Left lateral orbitofrontal (12.6%)

Is it kosher to use Haskins Pediatrics atlas for reporting results in group analysis of scans registered to TT-N27? More pointedly, is it fundamentally wrong from technical point of view?