?! After debugging for awhile, I got it so that PanedWindow doesn't cause the rightmost widget to tear! I had to disable the resizing binding on Turtle to make it work. 

However, now it seems like the canvas is no longer centered. Is there anyway for me to get around this? Maybe I disable the binding on the demo side and re-adjust the center when we initialize the canvas?

I want to make sure it works for you guys first before digging into it.