I'm working on an ultra-wide Monitor (OSX) with a width of 2560px. When starting Subform it will go "fullscreen" which is way too big for me.
I would prefer if it started with a maximum width that fits the Artboard preset default of 1024x1024 + all other UI elements which is about 1900 or so.
Also it would be nice if it remembers the size when restarting.
Agree that remembering the previous window size is the ideal behavior—consistent with how most apps work. Thanks for the input, Thomas.
A few things before I can implement:
On the first run, should we still maximize? Or start with a small size that works on everything (including my tiny macbook air)? If the latter, what is that size?
When remembering window size, which window are we remembering? The last Subform document that was open? A different size/location for each Subform document?
If on a per-document basis, are we doing that on the machine (remembering size based on the file path)? Or should the "window size" information be saved in the file itself?
What happens when trying to restore a size that's impossible because of a change in display configuration (external monitor removed or file opened on a different machine)?
What's the behavior when opening a new document or a document that hasn't been seen on the local machine before?
Welcome to my life, ya'll. = )
Based on my experience with a 2560x1600 and 2560x1040 resolution monitors I can tell you that all apps sort of degrade with that many pixel. There is a different point in each app where the extra space doesn't provide anything extra but just starts spacing things too wide apart.
Anyways, I would probably prefer it started with some kind of max-width since after about 1900px you don't gain anything. Can't say much about height since the monitor is capped is at 1040 and that is too small. 
Can't say much about the other things.
Also, it is fine to start in Fullscreen. Just my personal preference for apps not to do that.
I hope I didn't give you the impression that I'm not interested in your problem --- I definitely agree that it's a sub par experience.
I have the opposite problem on my 11" macbook air, where apps or websites assume they have tons of space = )
It'd be great to resolve this somehow in the future, but it's complicated and doesn't sound like it's preventing you from using Subform --- as such it's a lower priority issue that we can fix after making the world's best layout engine and typographic controls =P
Thanks for your understanding and patience!
I think we work in a different specs, but different from the most users: I work with two monitors and can answer some questions, based in my use. If Thomas answer too, you can compare. 
Yes. First run, the software don't know how you like, so, go to fullscreen. Or, if the resolution is greater than 1920, fix in 1920x1080.
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The last subform document that was open. One (lastest) for all.
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Snap on the biggest resolution avaliable.
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All that other questions are useless since this option if per soft, not per document.