Quote - > Quote - It also means that you can't load old scenes made in old Posers which had no fixed render sizes (render into preview window), unless you undock. That's a pain.

How much older are you talking about?  Poser 7 worked this way for sure, and I believe Poser 6 did also (with the band showing render region).

Poser 6 and 7 had a floating preview window, and the dimension of it were saved with the file. If I made a CinemaScope frame, it would load as such later on, even if I didn't  fix any render dimensions. For this reason, all my files don't have fixed render dimensions, they render in the "Match Preview Window" mode, since the preview stayed in the size I gave him.
Now the preview window is docked (a good thing, except this problem), the "Match Preview Window" mode I've been using for 5+ years has become useless, because the preview size is fixed, and depends on about everything except artistic choice (and changes each time you open or close a window, like the library, for instance)...

So yes, don't everybody try to tell me one can work like this, indeed one can, but I still consider this is a regression compared to before. I was forced to undock my preview window, because else it's just too much hassle to load old files (once again, because of the "Match Preview Window" render size setting I used extensively) .