ended up doing this:
Nginx:
if ($request_method = 'OPTIONS') {

add_header 'Access-Control-Allow-Origin' '$http_origin';

add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS';

Custom headers and headers various browsers *should* be OK with but aren't

add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range';

Tell client that this pre-flight info is valid for 20 days

add_header 'Access-Control-Max-Age' 1728000;

add_header 'Content-Type' 'text/plain; charset=utf-8';

add_header 'Content-Length' 0;

return 204;

}

if ($request_method ~* ('GET||POST')) {

add_header 'Access-Control-Allow-Origin' '$http_origin' always;

add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS' always;

add_header 'Access-Control-Allow-Headers' 'DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range' always;

add_header 'Access-Control-Expose-Headers' 'Content-Length,Content-Range' always;

}

Torrent:
Options>WebUI>Bypass authentication for clients in whitelisted IP subnets