Okay, this device seems to suggest that multiple pulleys CAN be used to ratio up the effective weight. This advertisement suggests to me that I can load 210 lbs on the stack and then leg press 420 lbs., hence the 2:1 ratio. You guys agree? It's been a long time since I've done pulley problems, and thus I cannot visualize the distribution of forces just by looking at the image. So, I'll look into this particular problem later, when I have some calculating time. Cheers.