Gives you 100mm (4") more sail height.
Replaces the woven cloth cap that takes the top of your sail with one that doesn't slip or move around.
This is unproven, it looks like it should work as the load is in the right direction but there is a whole heap of tension on this part it may well split the laminations anyway.
Print it out at 100% infill is my recommendation, it's not huge so won't take forever.
Clear out the cordage holes with a 5mm drill bit.
Take her out for a blast and see if you can break it :)