I also use the mast to the front when going downwind. Sometimes the board pushes me leeward and I feel like catapulting but that feeling gives me more downwind angle. Usually this happens when I sheet in the sail abruptly. It is a scary feeling but very cool.
So what you are saying is that I should
stick my butt at the back of the board bringing also the sail (raked back) as going upwind?
I also tend to press the front foot instead of the back for more control and angle.
I will try using the back leg with more presure.
With your technique should the sail be also sheeted in?