[SR-Users] Balancing Asterisk

Hello all, I've read as many of the asterisk balancing threads as I can find. Either my situation is unusual or I simply haven't understood anything I've read. In short, I'm building an web/phone mashup which uses Asterisk's AGI to get its work done. My only users are on the PSTN connected to Asterisk through a SIP trunk provider. So presently, in and out through the same trunk, apps live on the single Asterisk box. My goal is scaling and failover. I don't have any need for cross talk or transfers between the asterisk instances, and the algo's in dispatcher seem fine. It seems to me that I should be setting the sip-router up a replacement for the existing peer in Asterisk. What leaves me scratching my head is how I then register the sip-router with the upstream provider. Alternatively, if I use the sip-router as an outboundproxy from asterisk (which seems like it's going to take some hacking to make this work in 1.4), doesn't this now mean I have multiple UAC's trying to register for the same name? Can someone set me on the right track? Thanks, Andy Lippitt