Two dozen 4" screw, another skin of ply on the lower rear and another pair of hands, and this contraption should be ready to do ball joints tomorrow.
Top and bottom, there are two 4x2s morticed into the uprights, with 5 layers of 150mm wide ply end-on and a further full-width ply skin either side. The uprights consist of a 4x2 and a ply outer skin. A 30mm 3/8" square steel frame and some offcuts of 4x2 dictated the dimensions.
Wood can provide excellent stiffness - see this video (http://www.youtube.com/watch?v=LyyPHxPgGHg).
That's something else I'd like to build. 
Improvements may include a steel strap around the circumference, a vertical sliding table and a flexi work light.
I considered a £55 6t steel press off eBay, or £21 at the local garage if I just take the wishbones in but making this was a lot more fun!
I may end up spending more than both of those figures put together, but the satisfaction of (hopefully 
) doing these myself must be worth at least half of that. 
Tomorrow, I'll get the van back into the garage and try out the Arcan jack on it.
A classic example of learning from one's mistakes.
