Bill; I run my Series stereo into the F-2B and then go mono out. The point is this; the sound coming from the neck pickup is significantly different from that of the bridge pickup, thus the preamp EQ setting (bass, mid, treble) that is the sweet spot for the neck pickup is probably not going to be the same as the sweet spot for the bridge pickup. Thus I have dialed in a separate EQ for each pickup that, taken together, enhance my overall final tone. For instance, because of the different tones of the pickups, I may want to take some mid out of the neck pickup portion of the overall tone but add mid to the bridge pickup portion. Then when I'm playing and I bring up the volume on the neck pickup and reduce the bridge volume, the change in tone is more what I'm going for than if I made the same pickup volume changes going into a single channel preamp. Another example, I may want to add a little high end to the overall sound, but maybe I would rather it be the cleaner high end of the bridge pickup than the dirtier high end of the neck pickup. So, having thus EQ'd each pickup, I then come out of the F-2B in mono and go to the SF-2 to use the parallel mono mode for my final tone shaping of the combined signal, because at that point in the process I'm interested in smoothing and balancing the overall curve. It makes sense to my ears. It's been a while since I've touched the settings on the F-2B; where they are now seems to be working well. When I do make a change, it's to the SF-2 and it's to accommodate the room, mainly small changes to the gain controls. Of course that's where I am now; a year from now, who knows? So yes, I do think there is a point in going stereo into the F-2B and mono out.