One of the MOST important things Dennis stresses on liner installations is that it MUST be done on a sunny day above around 75F or so. Both are a requirement for proper stretch, so just 75deg F on a cloudy day will not be the same, SUNNY makes that liner warm up an stretch out properly. It makes ALL the difference in the world!! Start early enough in the day so that it is sunny and warm thoughout most of the fill process as the evening and cooler temps will make that liner get more stiff as the temps drop and sun is no longer on it.