Yup!! I do things mostly the same, make sure the components are square and then get them as square as possible to the bus, but when I build something "into" the bus, with the walls as part of the structure, it gets fun
I have learned one thing that is key. Just keep moving forward and don't obsess over the little stuff. In the end, your family isn't really going to care if there is an 1/8" gap here and there.