QoS over redundant routers..How do?

[detsh]

Hello,
we have two internet lines. Both routers are reachable over one cluster ip address. This is the default route for our firewall. The primäry line is an 10MBit and the secondary is a 2MBit. Each router has his fix line (Router 1 10MBit, Router 2 2MBit). For our Firewall Cluster is it one address.

How can I define in topology the right speed for the interface in QoS tab?

Should I define 2MBit or 10MBit?

I studied the QoS docu, but cannot find anything over this theme...Is it really so rare, one big line and one small line to the internet to have?

I hope for an idea.+

Thanks

detsh