My 8000 BTU AC will get down to 60*F it's not quite as cold as I'd like (50-55*F) but but it's enough to get them through those two or three difficult months depending upon the weather that year. The only difference in the setup for summer is that the input fan is infront of the AC output instead of the window. The humidifier tube stays plugged onto the duct just as it is now so the AC air doesn't come in all desert dry and cause the lids to drop.
My humidifier has a large screw cap opening on the bottom and a plunger type thing that bubbles when it rises up and allows more water to come out. But if there are any concerns with leakage by drilling a 1/2" hole on the top of the humidifier tank where the handle is then I won't bother trying it. I can't risk flooding the condo downstairs... again!