I am building a new 1.5 (Metric) tonne capacity tipping body for a small van. My question is concerned with the strength of the main tipper framing beams which run the length of the van body and consists of two main beams, 3.3 metres long. I would like to replace the existing 3.3m long 80mm x 40mm x 3.2mm Rectangular Hollow Section beams which are laid on their stronger (40mm) x-axis, with 125mm x 65mm Parallel Flange Channel (PFC) laid on the weaker y-axis, in an inverted 'U' or 'n' fashion. The thickness of the web of the PFC is 5.5mm and both the parellel flanges are 9.5mm. The Second Moment of Area of the y axis of the PFC is 80 cm4 (Stronger x-axis is 483 cm4) The Second Moment of Area of the RHS on the x axis is 57.2 cm4 (Weaker y-axis is 18.9 cm4) The two PFC beams are bridged perpendicularly with RHS welded across both their ends. Outriggers are to be welded onto the outside face of the PFC ('n' channel) with additional mini triangular gusset plates welded inside the PFC, that correspond with the position of the outriggers as I am worried about the PFC 'flapping', or deforming with a large point load on the outside edge of the middle of the tipping body - I would suppose deformation here would relate to the first moment of area, as the force would be applied as torque across the section, rather than perpendicular to it, but I do not know what this value is for the PFC. Also inner connecting bearers will be RHS that will be triangulated in section, so it doesn't stress the PFC. Will the new 'n' beams be strong enough, or be as strong as the original Rectangular hollow section? NB: Sorry about the metric units...but you get the idea!