How to assign a scratch disk / render drive for large Gigapixel .PSB files?

Hey Klaus, trying to create a multi-resolution Gigapixel image. The file is a 60GB .PSB I'm on MAC OS X Yosemite 10.10.3
Several hours in KRPANO gives me an error that I am out of memory and space. I have a 12TB scratch disk/render drive that I would like to assign to KRPANO. How does one do this ?