To be a comprehensive site solution, IPB should have a simple setting that allows you to set the portal as the home page.

It only requires making one file change, and the documentation states that a tech can do it for you.
http://community.invisionpower.com/resources/documentation/index.html/_/documentation/administrator-control-panel/portal/manage-portal-r273

Just to expand on that, you can use said article to make nearly any application the default one upon visiting your site. :)

As Colin has said, its a tiny file edit that will only take seconds (that file is not encoded on a 'encoded' board either)