After doing more debugging I found that the request was being sent as a GET even though I had explicitly set it to post. Moving the data type to json, from jsonp let the request be sent as a POST, which resolved the issue. However this causes an issue in IE where the request is not sent at all due to the request being sent to another domain.
amplify.request.define("searchPostRequest", "ajax", {
url: "http://leServer:9200/people/person/_search",
type: "POST",
dataType: 'json',
contentType: 'application/json'
});