My problem with the mounted fish feeders, and this includes the smaller/cheaper TH feeder you were referring to (which I have one of), is that they don't have true directional slingers. They have deer feeder slingers with plates that just drop the fish food straight down on the 1,2, or 3 sides that are blocked. This can drop a lot of food straight down at the bank, and it probably won't get eaten. If you set a post out in the pond to mount one of these feeders, then it's gonna be a PITA to keep those 16 smaller hoppers filled.
Also, squirrel's love to chew on plastic hoppers.
