Evidence of Leftie?!

I noticed, in this photo of my son, how he uses his right hand to hold the pen but then his LEFT hand to do the directing, as the primary hand for detail work. I think he'll be a leftie. He's only sucked his left thumb since birth and while he seems to be ambidextrous in a lot of ways, I think he favors his left hand for doing the most precise work, as his primary fine motor lead. He was holding the pen end and then using the tail to drag it along the board to see if he could write with it, or scribble, this way. He was essentially using his left hand to write with and his right hand for balancing: