Added stress test, corrected per-request header config.
Apparently using underscores is a "special" mechanism for HTTP headers, and requires adjusting nginx to allow such things. Might as well just recommend using hyphens, which get converted to underscores anyway.
The current test just hits a listing of 20000 files against p4play. Returns a 2.5 MB response, which doesn't seem to cause problems (yay).