A normal leg is composed of three parts: the outside tube that mounts to the trailer, the inner tube that moves up and down due to the turning of the screw, and the inner tube that is free to slide up and down and you use to adjust for uneven ground.
If you drill a hole in the outer tube, the inner tube is still going to be in the way of getting grease to the screw, unless you've drilled high enough for the inner leg to be out of the way when it is run down with the motor.
Howard and Peggy
"Don't Panic"