I can tell you that the more surface you can heat, the easier it is to stretch the liner--and the less any one area is stretched. I had very good luck with the hair dryer. Only one section was too tough, so for that I used a heat gun on the low setting...VERY quickly! I don't recommend the heat gun but I could not get those last 3" back in the track without it...but it left the liner looking uneven there. Oh, well, it's an old liner in its twelfth season with 4 patches already and a lot of fading...as long as it's not leaking......