I think with how many trailers are left at ramps vs how many thefts there are the % chance is still pretty low. That said, any security I guess can be a deterrent for the casual thief but if a pro really wants your trailer/boat, I guess they're probably gonna end up with it. I use a wheel clamp and hitch lock at the ramp, with the addition of a chain and padlock to a post when at home. I've come back twice to the Dry dock ramp at Tweed around midnight with the first time a bunch of kids hanging around my car (only one there) and the second my hitch lock had been beaten out of shape. Had worse happen at my place in Capalaba with neighbour spotting a car load of blokes turn up one day to check my boat out and another time my anchor got stolen (kids I guess).