Having worked in an upholstery shop that replaced quite a few of these tops, due to the width of the material that was available the tops that were put on these didn't have the usual seams on each side of the top, but a center seam that ran down the center of the top from front to back, these seams were not the usual "overlap" style seam, but were a "french seam" that had the two halves sewn together, then folded back on each other at the seam, & then sewn down each side of the center (from the backside), resulting in a slightly raised double stitched seam in the center of the top, these were sealed with a bead of silicone over the resulting stitching on the backside of the seam.