Awesome! I keep my a/c running 24 hours, my plants love when it gets down to 68 during night time
One thing about these a/c units; they never cut off (at least the fan doesn't). I was worried at first because it never stopped blowing but then I figured out the condenser cuts on and off. (Thought it would be more like a home a/c). Anyways, you should be fine with that exhaust setup and 78 degrees is beautiful.
One more thing, I noted you put a carbon setup for the a/c? If you could post a pic of that, that would be cool. I just use a 400cfm filter/fan in my flower tent and a 200cfm fan/filter scrubbing out in the open next to my vegging girls so I don't have to worry about smell in the attic. I also took a small 12x12 air filter sprayed with lavender air deodorizer and taped it to the sheet rock in the attic over the a/c exhaust just in case
Hope all goes well, looking good so far from what I can tell. If you need anything else just shout! Take it easy.