[Plugin: WP Super Cache] Using the “Super Cache” feature with non-apache servers

Heya,
I’m running nginx, and would like to setup the full super-caching functionality of this program.
I’ve currently got the program working in “on” mode, but nothing is being written to wp-content/cache/supercache. Files are being written to wp-content/cache though.
I’m capable of writing my own rewrite rules if needed, but does anyone know why supercache files aren’t being written.

Here’s a screenshot of (most) of the configuration page as I have it.