Adjust the duct tape to establish a 21" beam on the Sonnet 16 and a 23" beam on the Sonnet 18. Make additional tape adjustments to establish a smooth inflated "gunwale" line. After you are satisfied with the shape of the hull, trim the excess hull material down to about 1" past the inside of the inflated gunwales. Glue 1" (25mm) wide 10oz PVC strips next to each of the duct tape sections. The PVC strips should reach to the top center of the inflated gunwales. Once glued in place, remove the duct tape. These permanent strips will hold the hull shape while the deck is being attached. Insure that there is some tension in the strips Note: No pics are available of the PVC strips at this time.