Perhaps I'm picking at nits with this one, but to my eye the hook looks a little far back in relation to the bottom chain link that it depends from. It would be easier to make a nice rotation for the hook if its hole were centred in the z direction in relation to the bottom link. Then there is the question, is the hook ever going to need to be rotated? If not then the hook and the links could all become one group/obj, and then it's probably not that important if it is out by a little bit.

Personally I think I favour keeping the hook and links as separate parts, so that they can all be articulated, but that does add quite a bit of work to the rigging. The subject of rigging chains is quite an interesting and complex one. There are two was to do it, a realistic way, or a fudge.

The complexity derives from this fact, an actor normally only has one fixed pivot point, but when the link rotates on the xAxis the ideal location for the pivot is in one place, and when it rotates on the zAxis the ideal place for the pivot is at a different place. It takes a bit of fancy footwork to make the pivot point change depending on which way the link is rotating. On the other hand if the links only need to rotate a little bit, you can get away with the fudge of placing the pivot half way between the two ideal points.

Sorry for the burst of technical diarrhoea. I got quite involved with rigging chains a few years ago. I just hope I can still remember some of it now.