I ran that way on my CB750 when I was more of a hot-shoe, and they reduced the steering effort when rapidly transiting side-to-side. But when touring, this eventually didn't work out so well, as the water during rain took MUCH longer to scrape off the discs, so it amounted to less braking at first, followed by too much braking a second or two later, made heavy traffic in the rain very unnerving. I swapped them back to the top again and it worked much more evenly. Eventually I went back to one caliper (when I found some good brake pads again) and never looked back.