I don't have any set figure for how rich to tune on the ground because I like to sneak up on a decent setting during a few flights and see how the engine reacts to changing fuel levels and attitude. First flight will be set so it's just barely out of a 4 stroke and if it doesn't want to take off then the engine is too small for the model . If it stays noticeably rich for a whole flight doing some manoeuvres like large loops then I know I've got a safety margin to lean it out a little.

With my Rossi 45, it flies around level in a 4 stroke but as soon as I bring the nose up it goes into a very strong 2 stroke which gives some idea of how much they can lean out. If I did the usual of richening a couple of hundred on the ground it'd be way too lean doing loops etc. The ultimate test is when the tank is nearly empty and doing the longest climb as near vertical as possible.