I'm in the process of building one out of some steel c-section . I had the steel donated to me from my work (part of some old framework our new CNC Lathes came packed on).

It doesn't look too hard so far. I've welded the frame up already. The dual cab ute I'm building it for has a tray on it that measures 1.6 metres long and 1.5 metres wide, so I've just copied vethat. I'm just waiting (saving up) for some aluminium checker plate to bolt on for the liner.

What I have thought about and will probably design at a later date is some drop-sides for it. I will build them from thickish gauge angle iron and cross brace them simular to vehicle ramps. I'll mount them with quick release hinges and drill the ends so they can be joined together. So when I remove the L & R side and can join one to the front and one to the rear gate so I have have two 3.1 metre ramps to load stuff onto the back <img src="/forums/images/graemlins/pfft.gif" alt="" />

I will post pics when I finally get my funds together and it looks less like a dodgy rectangular frame.

One tip I got from work is to weld it together with a stick welder rather than a mig welder. Stick welds are meant to penetrate deeper and be stronger.