Bantams or large fowl? I hate to say it because I greatly treasure everything Mr. Urch has done for purebred poultry, but I had ~15 Dark Brahma Bantam chicks from him last year and every single one of them had Vulture Hocks. Just my experience and he may have dealt with the problem, but just a word of caution.
Very few dark bantams that are completely free of VHs. I don't know of any Large darks with them? I think the only big birds with them are imported birds or birds that have been crossed to other breeds to get a new color, and of course birds out of these two examples. The three large varieties typically shown have clean hocks. AND if you look at MANY of the dark bantams shown.....there has usually been some heavy duty plucking going on. Jimmy Rust has some VH free bantams...type is not up to Buffs and Lights though of course(Jimmy's birds are farmed out at the present to another gentleman). John Beamers in Canada has some excellent Dark bantams. I believe he got some from Greg Williams who had eliminated the VHs in his line of bantam Darks using sports from his Black project. Greg of course no longer has birds.
Tim