Add an occlusion map as a secondary map in the standard shader

This problem seems so trivial that It's so immensely frustrating that I can't find an answer that works how it should. I've made a model in Blender to import into Unity, which works fine. The albedo map and the normal map are both scaled x5 in Unity. I also made an Occlusion map by texture painting in Bklender.

The problem is, the occlusion map is already the correct scale. If I add it to the "Main Maps">Occlusion setting, it gets scaled x5 and everything is in the wrong place. The secondary maps have no option for an occlusion map. If I move the main maps into the secondary maps section, it looks too bright.

I have no experience with writing Shaders; I'm mainly a game logic programmer.