It's only fitting that the older sister put her two cents in, as well.
I had similar thoughts when I started on my PM program. PM works, so I recommend going with it. As Lisa pointed out, you can back off at any point to stop growth and continue on a maintenance dosage. The amounts of PM you'll need will have to be determined through experimentation. Ramp up from one capsule a day the first week, then increase to 2/day the second week, etc.. Continue until you feel your breasts getting sore which indicates that growth has begun. Then, just sit back and watch them grow.
You'll have lots of time to figure out what you want long term - A, B, C, D, OMG! I've increased my target to a small B, so any goal you set today may very well change tomorrow.
The other thing to keep in mind is the possibility that you will experience a drop in your sex drive. Is that a problem for you? To maintain male function, I take a 7 day PM break every month to check out the plumbing and have that special love session with my DW.
Yes, there's still some male gender identity buried in there somewhere.
Good luck on your breast quest,
Clara Kay