Traffic Shaping & QoS for VoIP

I am pretty new to MikroTik and I must say that I am pretty impressed so far. I have a RB450 in my lab hooked up to a a Ubiquiti Rocket M5, my plan is to deploy this configuration once I get QoS working properly and finish testing some other things. I am planning on assigning each customer a different VLAN interface on the MikroTik (this is how we are currently doing it on another platform) and then assigning their subscriber radio (Ubiquiti NSM5) to the corresponding VLAN. Currently I have QoS setup using >ip >firewall >mangle to match and tag packets based on DSCP and then I have priority set using Queue Trees.

The part I need help with is the traffic shaping part of it. I have a subscriber radio set to 8Mb Down / 4Mb Up and I want to configure the RB450 the same way so it knows how big this particular customers “pipe” is while still providing priority to VoIP. I am assuming this would be accomplished by using the “parent/child” setting in the queues. Has anyone configured something similar to this?

You may want to have a look at this:
http://wiki.mikrotik.com/wiki/Connection_Rate