4) double press the MOVE button to access the assign controls screen
THANKS! This was the part that I was missing. After I read this last night, I figured it out.
At first I thought it was going to take two effect blocks to make this happen (2 volume pedals, one on each path).
Later, I discovered you can set the min and max for the "amp volume" backwards, to accomplish nearly the same thing without taking up an effects slot.
The way the graphic always appears that the sources are coming from a single point is a large part of what was confusing me also. When I decided that that single line coming in was a "stereo" lead, I was able to make more sense of it. I think I have a pretty good understanding of it now.
Wow, this thing is SUPER flexible... but when you are using two signal paths with effects, and try to add any sort of pitch effects you can quickly realize the limitations of the DSP. It would be nice if each effect was assigned a number of "DSP blocks", of course DSP heavy stuff such as pitch effects would have higher values, and you could have a meter above your effects chain which showed the total number of DSP blocks available, used, and free. As you start to eat up your DSP, the meter would fill up to show you how hard you are pushing the DSP. Also this way, if you are "over" and cant add an effect you could see how many "blocks" you need to free up to make the resources available, and how many each other effect is using up.
The term "block" might be confusing though, because of the term is used for "effects blocks" already. Maybe just label it DSP or something.
Never the less, the HD500 is SWEET!