In the photo of the Spi fairlead you'll notice a yellow line, that is the spi tack line. Once the tack has been deployed the spinnlock cleat jams automatically due to the pressure. I drilled a 2mm hole through the top of the spinnlock cleat for the trigger line attachment and added the loop on the other end which the spi downhaul line is led through.
It is harder to set up than the single line system and needs quite a bit of tweaking to get just right but the Spi hoist is so much quicker and (easier) than the single line the extra hassle seems worth it.
As for Datchet I would love to attend but I wouldn't be able to afford the divorce settlement.