Setting volumetric window size at openWindow()

When defining a volumetric WindowGroup, I can set the defaultSize().

It is possible to set a different volume size when opening a window with openWindow()?

In my use case, I want to display potentially different models that are of different sizes inside the volumetric window, and I want to preserve each model's size. I would like to create a volumetric window that is optimally sized for each model.

Alternatively I could create a volumetric window that is large enough to fit the largest model, and then reposition smaller models inside the volume to be at the front & bottom of the volume, but I haven't figured out how to do that either (Post on that question)