If you want to change the sizes of the existing panes or change their maximum/minimum size constraints, you can use the paneconfigure method. For example, the following code changes the size of pane2 to 100 pixels and adjusts its minimum size constraint to no less than 10 pixels:
.p paneconfigure pane2 -size 100 -min 10
Notice that after you call the paneconfigure method, the PanedWindow may jitter and that may annoy the user. Therefore, use this method only when it is necessary.