See I'm never sure about that... for instance I know Gerstlauer usually creates their own rough layouts and sends them to Stengel for him to make them work (or at least that's what they did on Typhoon & their new mouse at Wild und Freizeitpark Klotten). I think it varies from manufacturer to manufacturer & ride to ride, and I'd be careful about saying that Stengel designs
all B&M and Intamin rides. He certainly does all of the engineering related designing of rides, but in terms of layouts,
I'm 99% sure that he doesn't do all of them. He does some, perhaps even most, but not all. For instance, Nemesis @ Alton... I believe that layout was designed primarily by John Wardley, with the engineering of it done by Stengel. We may just have different definitions of designing coasters though... mine is whoever is responsible for the layout, while yours may be the guy that takes that layout and makes it and the rest of the ride work. Either way... that makes the difference between a Premier, B&M, & Intamin spaghetti bowl even smaller.
- BB