Thanks for your additional remarks. In my case they kept the wider slot to insert the sail on the original foil and replaced only the part just below. I'm aware that Amel has this repair set but in my opinion it is not strong enough as the rod that goes inside the foil has a very hard job in resisting the torsion simply because of the surface area of the intersection that is way smaller then the size of the intersection of foil tube itself.
My foils are indeed 35mm and at the colllar it now measures a bit over 40 mm. Amazing to see what a new foil would set me back. I hope my solutions will keep me away from that headache.
As said before, the original repair on our foil was done quite poorly and I don't think Amel or its associates made that repair. Amel probably just supplied the parts.