One of my recent inspection jobs was a 5 million gallon water tank in Hesperia, CA. All of the vertical seams for the tank were done with a downhill progression using FCAW and had all of the proper documentation to D1.1. These were CJP welds and were to receive RT following completion. The contractor is very reputable and international.
My former boss at a D1.1 shop had some vert down spray procedures for 1/2" girders. I never had faith in them. They were too touchy. While I do not think he cheated on his WPQ's, I think the shop did not often follow the WPS. When I was an inspector, I used to shut down the production line for it. I once pulled a large girder off the line as a reject. When they questioned me, I grabbed a guy with a torch and said "Cut this joint right here". He cut through the weld, and it had about 50% Pen and was hollow in the middle. They had to splice that girder, but they never questioned me again after that.