In all my years of working in Randy's shop (including turning hundreds of venturis) the one thing I did learn is there is no simple "Chart" to determine what venturi is "best". The diameter of the hole is only one dimension in the piece. The shape of the incoming funnel, the outgoing funnel and the overall diameter of the hole determines the speed at which the air passes through the venturi and therefore the relative mixture of air and fuel that feeds your engine. As such, the venturi determines how much power your engine makes and at what RPM. Also determined by this little piece of hardware is the point of the 2-4-2 break and the "hardness of the break. Re: hard, or soft break. We frequently made sets of venturis in 4-5 different sizes so the flyer could determine which one made him happiest in his weather conditions! Lets not forget the position of the spray bar, and it's size, etc, etc.!
My advice to any one needing venturi(s) for control line use is to call your Guru, tell him what you have, and what you want and let him make the decision(s).
Ward