I have seen the foam idea cause more problems that its worth. If its put in the wrong place it can cause the angle of the wing to change. To get a good seal I use light weight wood filler agaist the wing saddle. I put wax paper on the wing and tighten down the wing to squeeze out the excess. When its dry I dremel the excess off the edges for a smooth finish. Then I ca the wood filler to fuel proof it. [8D]