Slide topper Fabric is NOT cut to your 29 inch length. The OEM slide Topper Fabric is cut for ALL possible lengths. When ordering a NEW complete slide topper, you only have to know the width, not the length. Length is for the out, not for front to rear. You always have excess that you have to roll up. Your springs do not care about the length of the fabric or how much you roll up before you reach your 29 inch width. Get the fabric that is 20 inches longer. When I cut replacement Slide Fabric, I cut the exact same width and Length as the OLD. IF no old fabric, then I still will cut for width and add that 20 or so inches to the length. Doug