If I'm one of the "some people" you refer to. I wouldn't bank on what I'm doing as acceptable. I barely make anything longer than an inch. I've never even checked anything for level, square, twist, etc. MY parts have virtually no precision requirement. Even when they do, I've found that nothing I do is as demanding as people act like it has to be. I'm making parts for me. I have pretty low standards. If it works, or I learned something, the project succeeded. Lol But if you're planning on making things 5" long, you're gonna have to sort it out. I'll leave the advice to those who are not in the "some people" camp. Lol
Edit: .0017"? Never mind. I don't think there's anything wrong with your setup, and I would move on with no further changes or effort.