Help with a 2 to 1 mechanical Advantage rig

Hey all! I’ve watched a tutorial recently on rigging a cable across various pulleys and having it lift a block using drivers and the curve modifier (for the cable). But what I’m trying to do is build a telescoping boom section (like a crane) that uses cables to telescope the innermost boom section. I have attached an image (it only let me add one). This is a typical method of doing telescoping booms, but I need help rigging the steel cable so that (A) the moving pulley drags the bend in the cable along with it, and (B) the cable actually retains its correct length, and (C) the innermost boom section that is attached to the base of the cable is pulled forward as it should be, via 2 to 1 mechanical advantage.

I assume this is doable in blender, but I’m going to need some pretty precise instructions if anyone is willing to take the time to help.

Thank you!!
Also, please note the boom sections in the images are cutaway views (mirror modifier removed)