What is the most appropriate weight before starting the MTF transition?

Should I start transition with weight, which is appropriate for women or for men and reduce weight later. What is the best for 43 years male, vegetarian and very active in sport to have the suitable breast development. I would realy like size at least c. And does it really matter, how much is the most appropriate weight before starting the MTF transition to have the best possible result and are perhaps some other factors, which will have influence on breast development ond feminising on generel.