The RPS flag all works perfectly for us too, it's just the filling of the "static" parameter.
Without the "static" parameter, the provisioning URL isn't visible in the GUI of the Yealink handsets. Not sure if this might have been an intentional change on Yealink's behalf with newer firmware.
Essentially what it looks like from what I can see is that if you don't have the "static" keyword, then the phone will request a provision from the URL once and then drop the url config. Which is where we run into trouble if we make a button layout change and then trigger a provision remotely the handset no longer has the provisioning settings.
It was all working really well for us, it changed around about the version where it was discovered that Vodia needed to parse the Yealink config first. it was at that same time that we pushed out handset upgrades too, so I never took notice if they keyword had changed in the template or not.