One thing that took me ages to find when trying to figure out why my own Height maps were crashing was a certain setting - I'm not sure if it's on FA though. I tend to use a mix of GIMP and Photoshop, but after a bit of research, it came to my attention that I had to check a setting that was called 'Background Colour' (which basically made it white and easier to render).
Furthermore, make sure you're 513x513 is in pixels and not mm or cm, that can be accidentally done too.
Hope this helps ^^