How often do you get enough thread in the ice on the first turn that you can spread that knob out and not lose the 'bite' that you started? In other words, when you are starting a screw and you turn it all the way you can on the first rotation, it seems to me that spreading that knob out creates too much leverage on the scew so that when you try and turn it, it pops out because it doesn't have enough bite in the ice.
I try to place screws about waist high so I can use my hip to hold apply pressure as I turn it.