Just some food for thought. If you look at a worn out set of sliders, you will see a wavey pattern-thick where wheels are, thin inbetween. So I got thinking, if there were no wheels, wouldn't the whole lenght of the slider absorb the total weight of the sled, not just the area between the wheels, minus the unworn area at the wheel location? If we rode on a hard flat surface, the wheels would hold up the rails so the sliders wouldn't wear at all. but we don"t. This could also apply too the front wheels at the curve of the rails at the piont of track first contact. What are your thoughts?