I finished my strongback the other day, and seeing as the inspiration came via here, thought I'd post a picture. Thanks to Bohdan for the first half of the calculations to work out the geometry (in an earlier post). The timber started out as 4x1 boxing grade pine - i.e. it cost next to nothing, but I had to clean it up. The hardest part (apart from all the maths) was setting up the mitres on the ends of the crosspieces. Every second cross piece is 2x1 to save on weight and timber. Seems plenty stiff so far.