This is resolved. Thanks for your time.

It turned out to be a PEBKAC issue... Problem Exists Between Keyboard And Chair... in other words this was entirely human error on my part. I had duplicate Host Name Mappings for the mydomain.com naming. It was resolving to my #1 site because I was explicitly telling it to. I didn't think to check the host name mapping section of my primary site.

Thanks for your help  -DavB (with egg on face)