Very well done Stage and your source is correct with respect to Reality, it is best enclose your scene when possible. Though I have many outdoor scenes that were not completely enclosed. Since I usually start my renders about an hour before I go to bed and let them run while I'm at work I can't say just how long it would have taken me if I were to have watched it.
I use some sort of dome all the time when I use GI in Maya or C4D, I've never used one in Poser. I'm working on building one and testing it out. If it works and you want, I'll share it with you.