The "Static child" is an implementation detail that should not concern you (you should really not even know it exists-- it should not even necessarily exist in the first place). I don't see how -f would be specifying the size of "the Static child window within the display area", so you should not be expecting -f to be setting the size of that control. Instead, I think the intention of the -f switch is to specify the size of the *display area* of the window (everything but the border), which is much larger than the 20x20 red box in your window screenshot. The fact that you can draw a 200x200 red box in a resized picwin that was created with -f 100 100 is proof that -f is specifying the (window size - border), *not* the canvas size to draw to. Because it's specifying (window size - border), you should expect the minimum size issue with *and* without -f.
Again, you can easily solve this by removing the border on the window.
