A cable should be fine for chops but you can also do them with med. balls or dumbbells.
Go to
http://www.prperformance.com/articles.htm
I have some examples of dynamic flexibility exercises for golf and in the rotator cuff article is an example of a PNF D2 pattern with a cable that may give you some direction.
The thing most people don't understand about flexibility is that it's not just a matter of how much range of motion you have at a joint, but rather how much you have at normal speed. Increasing ROM may require the aquisition of strength at end range of motion and adapting that range of motion to the speed of normal sports movement.
I have several clients that test "normal" during standard flexibility testing, but look restricted during a swing simply because they lack that end range strength to allow the joint to move freely.
Bill