I tried that and it may work well on a Merlin and is a good idea, but I couldn’t get it to work in an unencumbered way with my Wayfarer when tacking upwind. That dyneema has to stay well out of the way when going upwind in strong winds and the jib on a Wayfarer is quite large compared to a Merlins. But you try it, if you can and report back. It is probably a better way from the downhaul point of view if you can get it to work when tacking upwind. I have fitted conventional uphaul downhauls on a single bungee and single uphaul on both poles ( a V coming from the top of the mast just below the spinnaker halyard). When I pull the pole higher to raise the ‘in-use’ pole the other pole goes up as well but that doesn’t matter, it’s just sitting close to the mast in the lee, and not in use.