You change the size logic to absolute then change the absolute size to a different width/height.

The setting are now set.  And saved.

If you close the form designer window, and reopen it, the absolute size property gets reset back to 0,0.  This was its original "default" setting when it was originally drug on to the form. 

Per the documentation, it looks like we are doing this correct because we have set to "Absolute" but it still does not retain its settings.