14k corn-pro trailers come with a sicssor hoist. Every trailer I've seen smaller than that uses one or two cylinders.
I purchased a 10k, 6x10 ft dump. It used 2 cylinders, one on each side, and works great. Angle is either 45 degrees or close to it. Mine seems to work slowly, but it has never failed to lift anything I've put in it. I'm sure I've had it overload a time or two. Not sure that an angle less than 45 would always dump dirt.
How many cylinders are you using?