I am installing a 28ft round Matrix and have a question about the skimmer. The skimmer is a wide mouth and has a butterfly gasket. The install guide says to install the skimmer with the butterfly gasket over the wall and liner which means I would need to cut the liner before installing the skimmer. Is this safe to do? Most people say to install the skimmer and then cut the liner but that isn't what my instructions say. Can I cut the liner first without causing damage?