To me window size should be according to interior layout.
I see a few windows half covered with interior cabinetry. That looks like interference of the two (to me).
In my build I am trying to mimic a factory look - which is not a small aftermarket window.
I realize many are not looking for the 'factory look'.
I have gone with a slider door on my van. On my drivers side window I am using a window of very similar size.
The height of the drivers door window and the length of the slider window.
Just for symmetry. I get caught up on balance/symmetry... lol
The interior pieces are intruding minimally into my window space. In which its hard to have a large window and not have cabinetry impede into your/my window space.
CRL seems to be the most common and biggest mfg of van windows. That is what SMB uses I believe.
I am using CR Laurence.
This is the only pic of mine so far - my interior is under construction. My cabinet will go apprx 4" into window space... Argh!
But minimally compared to some.