Having trouble with custom variables

I'm new to Piwik but so far very impressed. I've recently been adding some tracking to a very simple Backbone app and have run into some difficulty around custom variables.

This app is running in an environment where I can name the clients ( and that gets exposed in another javascript object ) and want to pass that name up. So no problem right, custom variable. So I did the following in the router initialization:

      window._paq.push(['setCustomVariable', 1, "Client", kioskID, "visit"]);

and then later something like:

        window._paq.push(["trackPageView", '/trend/tap/'+ pid]);

For just simple brute force sake I've gone ahead and replicated the setCustomVariable command directly above a couple of the trackPageView calls and I'm still not seeing them tracked. Also I've changed between 'visit' and 'page' just for grins, still no joy.

and I'm not seeing anything under the visitors > custom variables tab in the analytics interface. Though I am seeing the title getting tracked properly

Any suggestions? We're running 1.11.1