The Haskins atlas is smaller in size than the TT_N27 or the MNI, reflecting the size of the brain differences in children compared to either 152 adults or Colin. The issue is really normalizing the pediatric data to the adult template or the adult data to a pediatric template.

You could try to make a nonlinear warp between the two spaces (Colin --> Haskins) and then warp the stat map or cluster mask to Haskins and try that. But I'd still be wary.

Many papers have claimed "willful ignorance" by just putting everything to an adult template and calling it a day.

I'll try to ponder it over the weekend and likely confer with some of the co-authors on the pediatric atlas.