I think you are trying to over engineer this Ken, and going with that convention and trying to make it the beefiest thing possible.
To determine stress in an element due to bending, you use the equation:
sigma (plain stress) = (M * C)/(I)
Where M is the moment, denoted by force times distance from pivot, C is the distance from the center line to outer wall of beam (would be the radius of dealing with circular cross section), and I is the area moment of inertia.
Since the moment of inertia of a multi beam system like you were talking about is pretty damn hard to calculate by hand, I can't do any bending calcs, but I will tell you this.
You know those posts that hold street signs up? I was able to use one of those as an RTI ramp one time. One end of the post was rested on an object, the other on the ground, I drove my drivers front tire up, and the post didnt' bend at all. I got out and scratched my head, I was sure it was going to bend.
I very well think you could do your design without the 2nd row. The yield strength of most of that metal is pretty high.