It's been drawn to my attention that some boats are being rigged with an purchase on the adjustable jib tack. In the example above, the black and white line starts on the forestay attachment fitting, goes through the jib tack cringle, around a block to a cleat. By going though the jib tack cringle, a purchase of 2:1 is created. The rule governing adjustable jib tacks is 1.7.4
1.7.4 The tack of the jib may be secured so that it can be adjusted while racing provided that no mechanical advantage is gained by the adjustment.
To comply with the Class rules, the line needs to be attached directly to the jib, and then led around the block to the cleat.
The class rules can be downloaded from the World Sailing website here https://ukmirrorsailing.com/index.php?option=com_content&view=article&id=585&Itemid=330