Hi Guillermo,
Good to hear from you!
The 'JC strap' is just one length of bungee passing through a 30mm block on the bow and with two clips to attach each end to the rear kicker attachment on the boom.
The limitations are covered in the Class Rules and the rigging description can by found in the Rigging Manual.
Both of those documents are available on the
Documents Page of the Class Website.
I use about 1.60m of 6mm bungee.