And sorry for the delayed response - I was on retreat! To answer the question about the amount of lean - it only takes one inch of lean to start or to go faster. For example, from starting and moving into first gear, you would check your posture, feel your feet, and fall from there. About the moment you feel pressure under the forefeet is when you pick up your feet. You balance into that lean, watching for signs of tension in your lower legs and feet. As you move into second gear, again, the lean is very subtle. Check your posture (as you run), feel your feet, and fall just enough to let the speed happen. And adjust and balance.
It doesn’t have to do with conditioning on how far you lean; that is more related to how long you can comfortably hold that faster speed. If you do it correctly, you should be able to hold it for a while. It does take practice to get that good form down, and in the process, your conditioning will improve. Give yourself time and patience and be consistent.
Hope that helps!
Certified Chi Running and Chi Walking Instructor