My pool had two openings, one suction, one return. I replaced the Intex return fitting with a standard Hayward 1-1/2" wall fitting, and while the hole was a bit bigger, it was only a little bit bigger and is well covered by the gaskets.
I originally left the Intex suction fitting, and tee'd that off of the skimmer line. I wanted to use it as a dedicated vacuum port, but the screen cover would clog up too quickly. I only used it once or twice as a second suction as it would kill the suction at the skimmer. Now that I have a suction side cleaner I will replace that fitting with a std 1-1/2" fitting and use it as the cleaner hookup.
There are a couple of pics in my install thread that show how I plumbed everything.
http://www.troublefreepool.com/threads/96641-Hayward-Skimmer-in-Intex-Ultra-Frame-AGP
With the new Hayward pump and filter, I have plenty of suction and hope to be able to run the cleaner and skimmer together.