My right thumb goes over the top but amongst other things I am an artist... so go figure and I am a highly visual person, drawing people and landscapes in my mind way before I get around to putting it on paper and all kinds of visualization process are easy for me.... but I am also almost ambidextrous, too.
�God is the basis of life, life is the basis of energy, energy is the basis of matter.�... Carey Reams
My left went over my right, however I feel I'm more balanced among the right and left-brain characteristics. I'm not a great artist, but I made some decent things during my days of art class haha. I feel I'm creative though, and definitely a visual person. I am also logical and very analytical (I got a minor in accounting, although I did not enjoy it, I was good at it).
I don't know if this matters at all, but I do some things right handed and some left handed. I am right handed at everything except golf and baseball.
Perhaps the ultimate goal is to brain balanced, to approach live not fixed from one direction or another but to be able to do what is best for each task and each creation from which ever direction is most suitable?