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you could also use a hole saw on a drill, to get larger holes if you need them. you will need to stiffen it though so it doesn't bend/flex during the cutting process just like bearfan said.
If its the rubbermade that is flexable then I would advise putting some external bracing on the container itself to give it more stregnth.. if its one of those garden/farm rubbermade containers.. I think there still brown.. then drill away!!!