Quote -  Heres the thing, I do a webcomic called Android, and I usually use just two panels per page set at 800x500 pixels. Occasionally I'll also do a full page and the Cover is always a full page. Problem is, that for the moment at least, I'm still having to render in P7 because P8 won't let me control the scene window size unless the window is undocked and floating.

I can make the window float and control the size, but then I have to offset it from the center of the screen or else it automatically re-docks and flares out to the largest window size  available. Which means that my window is usually obscuring one of the other pallets, which basically kind of defeats the whole purpose of redesigning the GUI if you ask me.

If I'm getting  your question right - the answer is pretty simple. In the upper right corner of the window are the docking controls pop-up. If you toggle off "enable docking" no matter where you drag the window it won't re-dock. That state change will be persistent every time you open up Poser or any room with that state chosen.