Any high dollar rod steel rod is an I beam, their weight to strength ratio is believed to be higher than the H beams. With most of the Nascar teams etc running them, I would be inclined to agree. Here's a pic of what can happen to a Eagle SIR rod when over stressed

If I was running an engine with a light piston and not revving it past 6500, I wouldn't be too stressed about running them. If you're swinging a heavy ol TRW slug, or you're turning it hard, that would be a different story.
AL...