I don't know about cutting steel of any significant thickness.
The potential danger, as I see it, is that a radial arm saw wants to 'climb mill' which is good, so far as the blade goes, but is tough on the machine if it is anything less than super rigid (which a radial arm saw is not).
The other factor is that the operator must then control the tendency of the saw to climb (towards himself) and at the same time, to permit it to do exactly that.
Perhaps you could alleviate this problem by ensuring that you bury the blade deep into the cut, almost to the arbor. This puts the down cutting force more nearly perpendicular to the table.
Clamping the work is a good idea, almost an imperative. Some kind of a feed mechanism to control the progress of the saw would be nice, even an acme screw with a some kind of inexpensive servo drive (like a mill feed).
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)