The trick is to not fix the top of the sail permanently to the top slider, but to make a tackle with dyneema with one end fixed to one of the lower sliders. Pictures are probably better than words, so....
Once the mainsail is raised and the distance between the lower sliders and the topslider increases, the tackle is tensioned and the top of the sail is fixed to the topslider.
|starting the hoist: lo and behold it works|
|Tackle is tightening and will be tight with sail hoisted about two meters.|
The dyneema rope is slippery enough to not get stuck and the topslider doesn't get stuck either.
By the way: the top block on the mainsail is a climbing block: very strong, light and durable and way cheaper than sailing-blocks.
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