An oriface like that would work. The size of the hole depends in how long of a land you leave in the plug.
My heavy backhoe trailer has an inline flow controll valve. It is set up so I can stand on the back and it will tip down to the ground. I can drive a dozer or backhoe up onto the trailer and sets down flat as the same speed it goes down with me standing on it. It is a little bitty valve with a needle control with a lock.