I am building a complete DIY 1/2 & 1/2 AGP/IG. It started as a 15' Intex AGP sunk into a 17' round (2' deep) concrete blk-lined hole (long story). I've now built another 2' of concrete blk above ground and am in the process if finishing the pool. Trouble is, no one makes a 17' overlap liner, so I had to get an 18'. I know I will have wrinkles and I am hoping to control the excess. Any thoughts on how best to do that? TIA!