RE: locking your differental
They only advantage I could see would be hooking up from a dead stop when you are going in a straight line on pavement or hooking up in general on a loose surface. IF you lock you diff and drive on pavement or other high grip surfaces you will damage you drivetrain.
Alot of people use a heavier weight diff oil to limit the slipping for better hook up on a track but totally locking it is a bad idea and is not necessary for bashing.