The fin box in your F-158 is bonded to the deck as well as to the bottom.
You can elongate the holes in the top of the board toward the front of the fin box until the fin screws line up with the brass barrel nuts down in the head of the fin.
Good idea to get some large dia. SS fender washers (31.75 OD with a 6-7 mm hole and some large rubber washer to go under the fender washers and seal the fin box from air being pulled down and onto the low pressure side of your fin.
You will have no leaks and will not affect the sturcture of the board at all.
The fin box is a large blocky cassette that gets bonded to the top and bottom of your boards hull and also
bonded into the foam interior on both sides and the front and back.
This is the easiest way to fix this problem.