a 5-foot harness would not have helped in this situation. We didn't do the harness thing, although we were terribly tempted. We already get enough funny looks for being an interracial family, the sneers from the "anti-harnessers" would have been almost too much to bear!
I haven't measured the harness, though it is less than five feet and as short as one foot. My daughter usually holds my hand even with the harness on. The harness is for those moments when she sees something that catches her attention and she must rush to it without notice. In those cases, I follow her and see what it is that has captured her eye. In some cases I will let her loose to play, in others, I will reel her in- depending on the situation.
We've gotten some funny looks and even a few comments from teen agers about the harness. But most parents ask us where they can get one.