Equirectagular to cube map transformation and per-tile cuve face

Hi,
I have this problem. I have a big Equirectagular panorama and we want to convert it in cube map, but if I set a cube face with a big size nona program exits with Precondition Violation error (the ouput image for the cube face is to big). Has nona some options to save only a portion of the cube face (for example only a quadrant)?

Thanks
Gianpaolo