Re: Fingers spread or together?
I think opening the fingers has its advantages and disadvantages as mentioned in the previous posts. I am viewing closed fingers as more of a disadvantage based on the fact that aikido is based on natural body predisposition of which one of the most popular is the natural arc of the arm. Similar to the fingers closed, this is not "natural".
Also, the tegatana is one of the most versatile and useful parts when doing aiki work. By closing the fingers, the sensation of the tegatana is diminished thereby losing some of its "usefulness" when doing techniques. If the fingers are closed, the sensation "transfers" to the fingers rather than the tegatana. It takes more "effort" to feel the sensation of the tegatana with closed fingers.
However, this is just my opinion. I think whether you do open or closed fingers, as long as the full sensation of the tegatana is still there no matter what you do, there is no right nor wrong answer.