The problem with the matte painting is not the geometry; symmetry in design is not a given. The problem is compositing 101, whereby the internal luminence curve and incorrect ambient bounces aren't aligned with the live action plate. If you had the elements separately and could recomposite them, you could sell this shot without changing the painting. That said, it is important to note that part of the loose style of these paintings requires the obfiscation of its nature by film grain; it is the reduction of the grain which really accentuates the textural differences between the glass and the live-action. When this shot is finaled, with the grain returned and balanced for Rec.709/sRGB, you'll see it really works much better.