remember cage it has to store the geometry , and the default for each link is 300 polys (30 x 10) , so 1000 link chain 300,000 polys  :woot: 

an actual program limit would be the variable sizes so it comes down to how long you want to wait and how much memory it will take.

I did find a paper on catenery for different anchor points but it also discussed different angular loads :(  it used an itterative method of changing A in the equation (that tightens or flattens the curve ) and then test fitting it to your known points.  It didnt seem that workable in poser python.