I just bought a 4-trac and after being in the water for only one ride it has some bulging above the extra holes for the slider fins that run the length of the board. (about 4 inches on either side of the extra holes running parrallel with the board). I didn't notice them before I used the board and am told that the couse is carbon fiber inserts in the board that are causing to bulge like this.
I'm no wakeskating expert but it sounds like bs to me. I would think its from not coating inside the holes enough or at all. The idea that the carbon fiber inserts are totally bs; carbon fiber won't expand.