Allows smartforms to be used on a SharePoint 2010 Forms-based Authentication site without logging in twice. Details on how to use this solution: http://peterblommendaal.wordpress.com/2013/01/23/k2-smartforms-and-sharepoint-single-sign-on
In this solution a few web.config changes are needed. You can of course edit the web.config files for SharePoint by hand, but it is better to create a feature for performing the changes on all your front end web servers on the farm. It's on the to do list, as is a management page in the SharePoint central administration to manage these settings.