What is the difference between these two skimmers on Amazon? (Hydrotools 8940 vs 8940H) What does Hay- Type mean? Will either work with any pool? How do I know if they will fit my pool? Would I be better getting a different skimmer like a wide mouth? Do you just cut a larger hole and drill new holes? I'm trying to order a new liner, skimmer, and start up kit before next weekend to get this thing up and running.