well...we HAVE a big unit in the attic, but it is 40 years old and leaks water. I have put a plastic cat pan between the joists with a submersible pump in it with a float, and a garden hose to drain it to the outside. It uses lots of power, cools only 'moderately' and is noisy. We use it when we have to. Replacing it would cost about $4000, and I can buy 2-3 more window units for ¼ of that.

We also have a lot of shade....