Cut and bend up 4 light channel straps and 22 deck support angles.
Fit the straps from the light channel down to the chassis as shown.
For fitting the deck supports, clamp an offcut of box section or similar along the inside of the chassis rails under the crossmembers to help level the supports. Centralise the supports between the crossmembers and tack weld all components together. When welding the deck support angles, it is not necessary to fully weld them to the chassis rails, stitch welding is sufficient.