Just finished watching it. The 4:3 footage and the 16:9 footage were perfectly joined. I looked really hard, I could not find any instance of frames not aligning, even in fast motion scenes like the door locking sequence (which I even freeze framed to verify).
I also looked to see if I could notice any drop in picture quality from the central portion to the top and sides, but it all looked normal. Again, it all blends well.
Your version allows us to see the most picture, like the star on top of the Christmas tree in Cratchit’s home (that would have been missing in the 16:9 version) and the full “Home Sweet Home” sign (whose right side would have been missing in the 4:3 version).
Thank you for your great work in this. This is going to be fun to watch at Christmas time.