Trixbox and a SIP gateway

At this rate I should make an Asterisk category!  Something I keep running across and forgetting to document is the configuration of the Cisco 1760 as a SIP gateway.  Specifically, I have the context set to "from-pstn".  I prefer this because it separates it, if such a thing ever becomes important to me.  The problem is "from-pstn" doesn't include the internal phones context.  So, the incoming call can't search the extensions, finds nothing in the dialplan and returns a busy tone.  I simply added the "from-internal" context to the extensions_custom.conf in the "from-pstn-custom" section.  Now the incoming call can find the group ringall extension and complete the call.