Anyway, I don't like the teardrop top cases and SDG said he could engineer the rear rack so that I could mount a motorcycle touring type box instead. They said that the box plus mount was 12 pounds and I often carry 15 pounds of shopping on my rear rack in a milk carton. So theoretically I could be carrying 30 pounds or so on a rear rack behind the rear wheels. I really don't think I "will" be carrying 30 pounds very often because I mostly want a righteous, lockable box to put things in when the bike is parked. Nonetheless I wanted to see how it would handle.
My impression was that when moving it handled normally, just as it does when I'm carrying 15 pounds. The one area where I noticed a difference was when it came to keeping my balance while going very slowly. But it really wasn't that different and, in truth, was a lot easier than riding double.