Hi Brian, the max resolution of viewport.renderToClipboard() or viewport.render() will be determined by the video card, it's an image generated by the GPU it doesn't really have anything to do with the monitor resolution.

The image generated by saving to .ai format is generated by the CPU, not the GPU so it's only limited by available system RAM (in v4 since it's 64-bit, v3 being 32-bit will have a lower limit).

- Michael