They look small an ineffective but they do work. I've hit two deer with the homebrew ones they used. One was a 2pt and it's horn hit a hood mirror and broke the plastic shell. That was the only damage.
The ones they made in house liked to squeak allot from the engine vibrations, the he shoots were always replacing hinge bolts and messing around with them. And they were really low to the ground reducing the angle of approach. They would drag on the ground on a moderately steep drive entrance.
The aftermarket ones look a bit better.