We did something this year similar to what David described using nylon strap to extend our telescoping arm, I would strongly look at using a lighter material than chain. Chain may be good option if your planning to lift several hundred pounds, but for what we encounter, the nylon strap is more than adequate, easy and cheap to acquire, low friction if you use UMHW rollers, and you can have telescope stages within a 1/4" of each other. Ours is shown
here .