Murray's has a diagram of a way to run longer lengths shock cord through some pulleys to give you more stretch during pitchpoles. Link here:
http://www.murrays.com/archive/25.pdf , look at "C."

I've now pitchpoled twice and broken the bungee I was on twice. Of course that was 30 year old shock cord so I wasn't expecting much. I've also blown over normally while on the wire and been tossed into the water still hooked up and the NEW shock cord did *not* break, so the previous breakages may have been to old shock cord.

Jim