The pergola before we bought the house. The back span is to far to go the single piece of wood is bowed down badly. The only thing holding this together is that they have screwed the plastic trellis to the wood about ever 6". They added a back support and put two pieces of lumber on each side of each column. Check out that pretty angle on the edges.
I failed to get pictures of my dad and Ric building this in February. Here is a picture of my dad with Ric during that trip. They did a great job!