The time has finally come to make the switch from Aperture to Photos and I'm having an issue... I've run Aperture with referenced masters, keeping the ~25GB library file on my system SSD and storing the 250GB+ of masters on an external HDD? Given that Photos can't support referenced masters I just purchased a 500GB SSD which I've installed in an external USB3 enclosure. From what I've read, the process to migrate an Aperture library is to drag it/open it into Photos and the app will do the rest, creating a new Photos library in the same location as the existing Aperture version. To this end I've moved the Aperture library to my new 500GB volume, but when I drag it to Photos the new Photos library creates itself on my system drive which is only 240GB in total size. Any ideas how to force Photos to create a new library on a specific drive?