Restrict length of curve

Hello,

I am trying to bend a curve using k2 components to simulate bars of a fixed length. When the curves bend into 3d, the lengths are increasing. Is there a way to limit this? or fix the length of a curve? The obvious option would be the length line tool however it seems to simply make the curve more rigid, rather than allowing it to keep its 'bounce' but restrict its length.

Any help is much appreciated!