I am sorry to tell you this, but I am fairly confident there is not a good solution. I treat a lot of implant-caused "uniboobs" (should be called symmastia), and so i am referred a lot of patients like you. I have tried everything, presented the cases to others, and no plastic...
Breast implants are not recommeded for patients less than a 18 years of age unless they have a congenital malformation and not just small breasts. Implant manufacturers will not honor a warranty if done "off label" at young age. Donald R. Nunn MD Atlanta Plastic Surgeon
Thank you for your question. At 350 cc you are at the maximum for your breast width of 10.5 cm. To go larger you will have to change to a high profile or alter high profile breast implant which will significantly increase your projection but make your breast with less.