We had the same problem with a drawing for a ramp to carry a mini crane, I didn't fancy the drawing from the moment I saw it but priced it accordingly and got the job and was then told I had 3 working day's to erect it. The ramp was built using forkheads and square timber supports with angled packers and another angled packer at the bottom to carry the boards to the ground. Who has that lying in their yard, told them the saw mill will take a week to cut all the required timber and they nearly blew a gasket. We ended up building it our own way from steel and I told the gaffer to take pictures every step of the way to send to his engineer so he could change the drawing to suit what we built. Our ramp turned out to be twice as strong as the original and I bet they use it more than the old one.