Hi,
Sorry but you are off the tracks if you are modifying mojoPortal code directly, that is forking it not extending it, and once you do that you will never be able to upgrade without losing your changes and you will soon regret going down that path when there is a new feature or a bug fix you want in a new version of mojoPortal.
You can add simple extra profile properties by configuration
http://www.mojoportal.com/userprofileconfiguration.aspx
you can also add UserControls that implement ISettingControl and you can add it to the profile page. Internally it can just return and empty string for the ISettingControl get value, but you can have your own logic for saving things, ideally in an UpdatePanel so your control doesn't post back the whole page. However that would require a separate save button inside your control or some auto save logic.
The only other solution would be to have a completely custom Profile page that you have in a separate web project of your own and use post build events to copy it up and replace the mojoportal profile page. It will still require you to maintain your forked user profile page, but at least then your code is in separate projects and you can still always pull the latest code from the repository and build your custom solution with the latest mojoPortal code. So you could still get upgrades and the latest code but you could never use the official release packages, you would always have to produce your own builds in order to include your custom code.
Hope it helps,
Joe