On the tiger and the tornado we used to run the tack line right down the stbd hull through a turning block and then to a block doing what is shown with the bungy there. Does three things.

1. it means you can pre-run the tack from aanywhere on the hull so if you end up reaching into the mark you can still set up for the rounding without sending the crew fwd.
2. Takes up all the slack in the halyard/retrieval line when down.
3. takes up slack in the tack line when the kite is up.