An easier and less expensive solution is to create a 2:1 ratio on the jibsheets by attaching two blocks to the clew of the sail with a (soft) shackle and then tie the jib sheet end to the jib cleat fairlead and feed it through the block on the clew and back through the fairlead and through the cleat. You can then decide whether you want to crossover the sheets and tie them off on the opposite tramp edge, in which case you will have two separate jib cleats, or have a continuous loop. It will require around 2-3m of additional sheet to allow for the additional loop either side if you are crossing over the sheet.
Benefits: Inexpensive solution and easy to set up
Cons: Higher potential for snags when tacking because of additional lines getting tangled. More weight on clew in light winds can affect sail shape (may be worth undoing for light wind days)