Quote Originally Posted by IGnatius T Foobar View Post
That extra stress is going to tug on the seam between the sides and bottom, which could cause the seam to catastrophically fail.
Only if the stress causes the material to exceed the elastic limit -- something that's pretty unlikely in a PVC fabric strained by only 1/4" over 16'. Also, because the dishing will occur prior to filling, any tension that does approach the elastic limit will be more likely to simply slide the fabric in toward the center. This could cause the wrinkling I mentioned, but not necessarily put a great deal of tension on the seams.