I don't know that the size is as important as just to get the weak point @ the fuse reinforced.
I'm really not sure but my fix was probably 2 to 4mm.
the problem is there is no continious reinforcement from wing to fuse.
All I did was cut 3 each 5 or 6 in long pc's for each side and go from the inside of the fuse thru into the wing.
My problem solved. Maybe I should say THAT problem. My problem may never be solved.
Hope this helps.