Your guns, your risk, your call.
Fair. We all choose our risk tolerance and hopefully use some basic sense in doing so.
With the sort of modern, overbuilt Spanish guns the OP is considering (Aya #4, Uggie), I don't think there's a big risk to using steel in them as long as the chokes are open. I say that mainly because I've done it with several different guns, have seen a number of friends do it, and not one of us has ever had an issue.
Now, I haven't done it with every gun in existence, and it's entirely possible and maybe even likely that some gun of this type, somewhere, will bulge with steel. So, some risk probably does exist.
Is that risk enough to keep me from doing it? No, because my experience tells me that the risk is small.
Someone else may have very, very little tolerance for risk though, and maybe it should keep them from doing it.
Like you say, everyone has to choose his level of risk and behave accordingly.
