Can I use my public IP for the ROOT URL when installing? It accepts the local Ubuntu IP just fine but I want to use the public one. I have the server behind a firewall NAT'd to the outside.

Ok, if you have the port forwarded, and have 'named virtuals' in apache, you should be able to use the name as long as you use a dynamic DNS client from some dynamic DNS server site and have apache virtual named, using that dynamic name acquired from the service. Hope that helps.

I actually own the IP so it's not dynamic in any way. I tried the httpd.conf trick with virtual hosts for both IP's but no go.

HMMM, I use dynamic on one of my servers and it works just fine for me, couple others are dedicated IP addresses. I use NAMED virtual, not IP virtual, so not sure. On my dynamic connection, I have multiple domain names that all server from the same single IP address, apache just sends it to the right place via the name not the IP. BUT I do not see why using the IP would not work :-/ but don't know for sure.

I'm not a guru on all the ins-n-outs of dedicated IP's, local IPS's, etc. But, I can offer this. If you're planning to publish any live apps in the apps store, it's very very likely that these apps will need to connect to your control panel for data. When they do, they will be using the IP address you setup in the control panel (look an apps config data screen, you'll probabaly see the IP address is some data URLS). This is OK as long as the URL's load the expected data. HOWEVER, AND THIS IS IMPORTANT... If you end up changing IP address, or moving your server, or otherwise ending up needing a new IP for your backend, devices will not be able to connect to your control panel anymore (because they have the old IP address included in the source code). For this reason, it's much much better to use an actual domain name so you can move things around as needed when / if necessary

Thank you David, I like that explanation and the reasoning behind it.