There are reasons to offset the tweeter laterally, although it's really not a big deal. Moving the tweeter to the center would require a slight mod to the crossover, and it's difficult to believe that anyone would have a strong aesthetic preference one way or the other. As for roundover on the baffle--that's just best practice. It minimizes diffraction effects caused when a wave (sound, water, or light) hits a sharp edge. You can ask Jim to square off the edges, but I will hurt him if he consents. OK--he'll hurt me. But don't do it.