I never worry until I need too or I would be nuts by now..lol..All Ducks I have had, rescues or my own all learn the ramp and no injuries..My Calls fly around my yard and land sometimes pretty hard on the ground..I guess precautions are good but being too overly cautious is pointless..
Injuries can happen to everything living..Heck, I fell on the ice and hurt myself. My Horse slipped and cut his leg on a tree/log..My Big Orpington Hen hurt her Leg flying out of the Coop..My Orpington flew and landed on my little Call hen and injured her neck..Casportpony helped me that day...
I get Ducks of all ages and they all learn the ramp in about 2 days..Ducks are like spoiled kids..They do what they like and protest things they don't ...lol
A wider sheet of plywood attached under the ramp works better..2 1/2 feet wide is great...All I say is bedtime and my Ducks zip up the ramp...Trained using a long stick..