What exactly about shoe trees in shoes prevents creasing? Is it the snugness in length? Or is it the all-around fit? A few of my shoes have a bit of space between the shoe tree and the top of the inside of my shoe - enough so where I'm able to actually push down a very tiny bit up until the top of the shoe touches the top of the tree. So I was wondering if the lack of space between those two parts is what helps prevent creasing? Or is snugness in length the main element when looking for a "perfect" fit? Both, perhaps? I'm assuming the trees should be both snug and completely fill out the toe box area, but I'm not entirely sure. Any thoughts?