I have the main Poser window on my main monitor, with everything docked, and use the second monitor for my floating windows such as the Library, Hierarchy editor, Python palette.

I have had no problems at all with this approach. Poser 8 remembers the positions of all my windows, docked and floating, across both screens.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)