There isn't currently a way to do this; the Ojay.HTTP.Request class
assumes that key-value pairs (provided as a JavaScript object) will be
used to form the body of the POST request. I'm working on a patch to
remedy this; I'll post an update once I've got James to check it over.
In the meantime, you can always use the YAHOO.Util.Connect class
directly; the Ojay.HTTP methods are just a wrapper around it.