If you've seen my other thread, you'll see I have a lot of experience in Taekwondo and a tiny bit in Hapkido. We teach hand grabs in our TKD classes, but they're nowhere near the level of what we teach in Hapkido (both to make them a bit safer to practice and to make them easier to learn). When I'm teaching in Taekwondo, I've run into a few issues: Working with a younger student who is double jointed in his elbows, I couldn't get many of the arm locks to work. Working with a student who has apparently done tons of pushups and torn up his wrists, he doesn't feel anything when in a wrist lock (but he does in arm locks). I can still take him down with the proper leverage and footwork, but he doesn't feel the pain compliance or the shock that I'm trying to cause. Have you guys run into people that certain hapkido techniques just don't seem to work on? What are your suggestions in those cases?