node.js node-http-proxy, proxy with url-encoded data

I'm new to Node.js and struggling to understand how to create a simple proxy for a given route/url.

I'm trying to avoid cross-domain issues for a front-end javascript logging framework by using a proxy with my node.js (with express) server. I'm using node-http-proxy module but I've run into a problem where the request.body is always JSON. I need to send url-encoded data, not JSON, to the logging server end point. So even if I send url-encoded data as the body of the request to the proxy, the proxy then sends JSON data as the body of the request to the logging server.

I tried converting the body to a url-encoded string in the proxy, but then it even more bizarrely prepends a quote character to the beginning of the body. One single double quote.

Thanks for the help. Here's my route:

this.match('/proxy/logging', function(req, res, next){
    req.url = build.logging_url.path;
    req.body = require('querystring').stringify(req.body);
    req.headers['content-length'] = req.body.length;
    proxy.proxyRequest(req, res, {
      host: build.logging_url.host
      , port: build.logging_url.port
    });
}, { via: 'POST' });

and my ajax call, in jquery is:

$.ajax({
    type: 'POST',
    url: POSTURL,
    data: {foobar : "foobar"},
    success: on_post_success,
    error: on_post_error
});