Where to set additional query parameters for tree lazy load expand requests with JsonRestStore in Dojo?

For a lazy loaded tree using JsonRestStore and ForestModel, where would I set an additional query parameter to be included in expand requests? I have declared the additional parameters in the SMD, but I can only seem to use the default values set in the SMD instantia开发者_Go百科tion, since expand events only pass the node id to the Service.js's "_executeMethod".

I've stepped through a bunch of times, but there is some magic that happens in a dojo._hitchArgs method in between the Service.js _executeMethod that makes the request and the JsonRest.js query(service, id, args) method. So basically how do I get my parameters in that args variable?

Thanks, -robbie