Expand "Custom Variables" up to 10 slots

Is there any easy way to expand “Custom Variables” tracking from the actual 5 slots up to 10 slots? Is this possible by doing a simple diff/patch?

From now on we use all the 5 slots Piwik delivers.

You can use 5 slots per visit and 5 per page. It’s not easy to add more since it needs more columns in the database.