Agreed on all points. Well said, guys. I should have been more explicit -- the BOF/CRS point works well for me, but certainly isn't for everyone. Some people are more weight-forward in their skiing style. Or as mentioned by Max and Heluvaskier, it's where their boots are forcing them to be. The BOF mark may then be too far forward. My wife is a good example -- she is an expert and powerful skater since childhood, and came late to skiing. As a result, her natural skating stance has translated into her natural skiing stance, which is low and forward. For her Supershape Speeds, the BOF mark is perfect, but is actually behind where the women's equivalent ski (Head Power One) would put her. For the Fischer Progressor 8, she is at the factory default mark which is well back of BOF. Everyone is different, but once you find the balance mark, you'll know it right away.
Todd, luckily you have a binding which allows you the ease of experimenting slope-side. You can try a couple of different positions all in the same day with just the flick of a finger. I've never used a Powerail, but it seems to be similar to the Dynastar/Look Fluid system. Dead easy to adjust.