How do I use jsvserviceclient.js with custom routes on service stack?

I started using servicestack javascript client for our application. Our webservices uses servicestack with custom routes (api.geni.us/v1/groups/list?format=jsv). The problem is that on the current client have no way to indicate that we want to use the query parameters (format=jsv) its currently set to always use the standard route(jsv/reply). Right now the only option we see is to inheriting from the client and customize the constructor but we are wondering if there is a prescribed way to do that before we go into implementing a version specific to us.