One our IP 27, CINNAMON we installed a 10,000 BTU unit under the vee berth and it did OK for that boat.
You can see photos here
AC and heat really make the boat great because when it is hot, we would simply dock and plug in and enjoy. THen in the fall, it would extend our cruising.
This past winter, and as in most winters cruising Bahamas and Caribbean, we never dock, so the AC is not used. We do not have a gen set, plus when cruising you really don't need AC/heat we find. I will say, AC was the first thing we installed on our IP 35 when we bought her.