I agree with twofosho. I think the strongest starting point is 2x3x1/8th tubeing. ive thought about torq boxes but dont have a plan yet how to implement them. hears my 2x3 job with notched floor and flat bar pieces welded to the seat stifeners. I thought about ex shaped gusets tying the conector to the rockers. thats just a thought right now. hears some pitchers.