and second members 210 and 214 may have different cross sectional shapes e g circular oval triangular etc the cross member 222 includes an upper planar portion 238 a lower planar portion 242 and a curved portion 246 connecting the upper and lower planar portions 238 242 in the illustrated embodiment the upper planar portion 238 is parallel to the lower planar portion 242 each of the upper planar portion 238 and the lower planar portion 242 include a smooth curved i e arcuate transition 250 extending toward each of the first and second members 210 214 more specifically the transitions 250 extend toward the interior faces 226 230 of the rectangular members 210 214 such that the cross member 222 meets i e intersects both of the members 210 214 at non orthogonal angles the curved transitions 250 eliminate any high stress concentration points between the cross member 222 and the first and second members 210 214 in other words the cross member 222 extends transversely between the first and second members 210 214 and includes mechanical stress reducing curved portions 250 to transition into the top and bottom of the first and second members 210 214 in the illustrated embodiment the upper transitions 250 have a radius of approximately 28 inches that is swept through an angle of approximately 90 degrees and the lower transitions 250 have.