There is a challenge at a beach I go to. Pay 2.5 euros for the opportunity to try and hold on to a bar for longer than 2 minutes. The bar is not fixed, meaning it can rotate. On a fixed bar I can hold on for a minute that isnt too thick. How much does this non fixed component act on your result? If I were to hold the bar with a pronated grip with thumbs over the bar , I would think that it is the same thing. Thoughts on this? Does anyone now the record for longest time holding on to a bar?
Overhand grip will focus on your forarms more than a underhand grip. Most people will be better at a overhand grip. Ref: http://www.umich.edu/~mvs330/f00/domination/main.html
Optimal position for your hands on the bar depends entirely on how your body is built. Someone with strong arms can do a vertical hang (narrow grip) easily and someone with strong back will excel at a wide grip hold.
Optimal would be a over and under grip (same as a deadlift) at slightly wider than shoulder width.