My response to why a lot of feed still falls to the ground..............as far as my observations, most birds make a mess when they eat, wild-birds at birdfeeders included.
The chickens seem to like their feed on the ground just like the scratch food that is fed to them. In the pen with standard size birds, the handing feeder seems to cause less spillage. I think that is because it swings if they try to push the food back and forth. But in the area with six bantam chicks the hanging feeder needs a big tray underneath to collect all the feed that they spill out. Those guys are just careless and don't worry about the cost !