All addressable object properties are available at runtime, weather autoset or not.
Generally, any objects/properties you can see in the XML are addressable. Hard-codeding is generally a problem of not being able to address objects, code, or properties that aren't exposed in the XML.
The issue you described sounds like either a timing problem or a script ordering problem. Check the following potential problems...
1) Commands are executed right to left, then top to bottom.
Example:
Result, A=C not the original value of B. Since the commands are on the same line, the right command is executed first, followed by the left command. In your case, if you wrote
Code:
window.size='100,100' a=window.child.size
You're actually asking for the size before its been changed.
To avoid execution order problems, I recomend always line breaking between commands.
Example:
result, A=B
2) Unoptimized graphical objects can result in rendering taking longer than the script that forced a redraw. Excessive image tiling in particular can cause this. Avoid using Rectangle styles that tile tiny image slices.
Example: You have a FrameStyle applied to a page that tiles a 1 pixel image to draw a border. The first line of your script resets the window's size. It takes 2 seconds to render the new size because all those tile positions have to be calculated. 1/2 sec after the first line of script fired, the script tries to get the size of a child object of that window, but it hasn't finished drawing so the child object hasn't changed.