Just for let you know I have been surfing my Extremely foiled Hull last week, and I moved back my fin at 1/4'', did not change the rails catching, moved it at 1/2'' it was even worst, but then I tried to move the fin up, 1/2'' forward and it changed everything! So you were right, there was nothing to do with the rails… I thought it was because the super thin rails were catching everywhere, but finally it was a fin problem like you told me.
I think it’s because I use to surf my hulls super far forward, so the ratio between my feet position on the board and the fin placement were not good.
So I ended up at having my 9’75 fin (super narrow tip) at 13 1/2 inches from the tail (at trailing edge)
Thank you so much for your advice, help and for sharing your knowledge !
Here is some photos with the board