I've been practising Aikido on a friend since my accident and have noticed a couple of things;
1. my left hand is my stupid hand
2. my left hand hasn't nearly half the strenght of my what right had
3. people don't expect the left hand to be the "go" hand
What I've noticed is that unlike with my right hand I seem to control Uke's thumb with my whole left hand - consume uke's hand within mine, whereas with my right I used to control uke's thumb with my thumb. It seems to me at this stage that the "new" found method or controlling ukes hand is far more effective in contolling the movement of uke.
I had to modify my left hand tech' as the strenght in it was sub par. So controlling the individual ment improving control more than improving strength.
Seems that I was missing the point in regards to controlling uke and his/her thumb.