Hi Steven,
I'm using another sample program (
http://www.voip-sip-sdk.com/p_79-fla...hone-voip.html) by Ozeki VoIP SIP SDK and so far it seems reliable and stable, plus they have a really good and helpful support team.

For me, the sample program is a big help because they provide very details configuration steps and source code explanation as well.
I think the sample program will be helpful for your project.
Good developing
