Tony, what is the single block on the bungee at the skipper position, stb hull , white line exiting?
That's the spinnaker's tackline.
It goes from under the front beam to a block at the shrouds, through the block you referenced and back to the shroud where its spliced to the block's center.
Normally tack lines are 1:1 but this one's 1:2 so I only have to pull halve the length, the line is thinner than standard to not add any extra friction while pulling.
