How do you set minimum EditorWindow size when undocked?

I'm working on an Editor Extension that lives inside an EditorWindow. It has a minimum vertical size of roughly 730 pixels. A decent minimum horizontal size is roughly 900 pixels. I've set this using the minSize property but now it appears that this makes docking the window a really untenable option: it forces the layout when docked to change.

I would really like to make this a modal thing: when Windowed, use the minimum size. When Docked, allow free resize (probably standard min of 100x100px).

I don't mind users trying to shrink down the window and hiding the content, I just want a reasonable first use size: make sure that when it opens it isn't hiding a whole bunch of content.

Any recommendations on how to do this? I've seen that there is a way to access the docked status of an EditorWindow but it isn't terribly kosher (uses reflection to grab an internal field). How should I best handle this?