This won't help with them chewing the rope through, but it definitely works to keep them off the feeder.
http://www.duncraft.com/Emerald-Squi...affle-Hat?shop
I used to have a tree next to my deck and I kept a tube-like feeder with sunflower seeds there. The squirrels would raid it like crazy until I bought the baffle. Then I amused myself by watching the squirrels come down the chain, try to reach the feeder, fail, and fall to the ground. They would try over and over and fail every time. It is much better than the round dome-like baffles as the top hat or witch hat as I call it is just long enough that they can't reach the feeder and it is slanted enough that they can't do much except fall to the ground. Some of the larger squirrels may be able to scramble back up the chain but I have never seen one get to the feeder.