I know, old topic..but just wanted to know that this procedure still works.
For reference, I did the "OBi-VoIP-Device-Attach-Legacy-IP-Phone-Workbook-v1-0.pdf" procedure.
I have an Obi200 and a Cisco SPA504G. I followed the PDF directions using option two (for any Obi).
Then I found this thread and changed the appropriate things.
Only mistake I made was before I found this article...and deleted the entry in Ext4>Dial Plan... so I don't know what the default is...but I put "xx." (minus quotes) from the first attempt (prior to the PDF procedure).
It dials out and rings with inbounds...so as far as I am concerned...it is a win!