I expand Poser across both monitors -- I tend to create scenes using almost the full size of the main monitor. For this reason, I move the camera tools, libraries, etc. to the second monitor. To do this, I expand the window across both monitors.

And, yes -- I experience the same thing that you do. I have to manually stretch the window out each time that I open Poser. But as it's only a matter of a second or two to do so: I've never been much concerned over the matter. Frankly, I don't know if there's a way to "fix" the problem.

Something To Do At 3:00AM