1020 DOM, and there uppers don't put much thought into it. Run something some what beefey and they will be fine. They don't bounce or drag on rocks so no side force is applied.But do you know what grade it is?
I know all steel is not created equal and with a family in the heep I can't take huge risks. From what I have read the a36 will bend easier than the a500/513 or 10 whatever DOM. For uppers I would not think this would be a big deal since once would be able to put a straight edge on it and verify if alignment was off for some reason.
is the square tube stronger, perhaps resist bending more, if mounted as a diamond versus a square to the CA mount buckets? Or does it not make a difference?