Dear Casey,

I think that it is possible, and indeed SDM has been already modified for combining one- and two-sample studies (see http://onlinelibrary.wiley.com/doi/10.1111/pcn.12185/full ). Of course two-sample studies and correlation studies are not the same, but this will probably be only one of the many methodological differences between studies (others being the scanning device used, the specific steps applied in the pre-processing, and etcetera).

Best wishes,

Joaquim