This is always a difficult decision for some. In my opinion, the best thing to do is have a thorough sizing session. I provide my patients with a range of about 3-4 implants that are appropriate for their specific measurements. I then have them try these implants on in a special sizing bra. With this process, my patients have been able to choose their own implants. I have found this to be the best method for implant sizing. Be sure to see a board certified PS in your area. They should be willing to spend the time with you doing this. Best of luck!
Without photos and breast measurements, and perhaps some photos of what you consider a goal size and shape, all I can suggest is to raise these questions at an in person consultation with a plastic surgeon.
All the best.
I think that the most important thing you can do is go for a consultation and discuss your goals and have an appropriate exam.
I have operated on a number of models, my first question is what kind "fashion or promo" also what is your goal in modelling. Once I know that I have a good idea of what shape and size is ideal