Hi Dario,
I noticed Moodle three columns view since I started working with the planner and I know it would be very helpful, if you notice Moodle has those three columns only in the planner view page, not in every page, this means that the three column view should be implemented in the planner package index and not in the theme as in theme-tupi (tupi has two columns).
The three column view is in my wish list for this package but I'm afraid I don't have enough time to do it now. I'll let you know when I do it, or if you can do some work about that yourself, let me know how can I help you.
