I know that when you order the extra a/c for the bedroom, they install double trusses adjacent to the a/c pass through opening. I would think if there were to be an issue it MIGHT be the extra weight on the single trusses in the back. I would hope your installer gave that the needed consideration. I'm sure if it would have been an issue, he would have said something about it. I think a/c back there is an awesome idea.