The minimum size of the form should not be allowed to be smaller than 600,400 (Width, Height) if it is resized.

In KFD there is the Form property "MinimumSize" - Of course this sounded like the perfect solution to the requirement...

However it appears that this is not implemented at this time. Or am I missing something?

When looking at the TypeLibrary it does not show this property. So is the only solution to watch the SizeChanged event?
Today is the tomorrow you worried about yesterday.