I was in a Spaulding class a couple of months ago, and we were shooting his steel targets. I don't know who manufactured them, but they were on 2x4s and the face of the target was angled down. We started out shooting them, straight on, at seven yards and had to step back to ten because we were getting peppered by spall. I don't know if it was from the target face or the base. We only fired a couple of volleys before we stepped back. I have a feeling that one shooter and one target presents less of a problem than a number of people and targets on a line.
I prefer to be at least ten yards away if I can help it. Our local matches don't allow for shooting steel any closer than 10 yards, and even then I have seen people cut by fragments coming back. Once, a bullet fired at steel in another bay came plummeting from the sky, seemingly straight down, and hit me on my trapezius, leaving a knot that lasted a few days. I'm glad it didn't make it to my noggin.