Oooh where did you find these leashes? I'm trying to find a duck harness and all I can find are the diaper ones.
Never actually used one before so I can't really answer your questions but I have heard of people who have used them.
We make harnesses and leashes that are JUST harnesses without the diaper part. Specifically for ducks and geese =) you can find them on our website at www.SewSammi.com/shop