375cc on a tall lean girl too bottom heavy? (photo)

Thank you for your question. I would recommend going 375cc based on your photos you should have great results. Best of luck.

Based on your photos you should have an excellent result following breast augmentation.  I also think a 375 cc would look just fine.  Since there is very little difference between 350 and 375 cc most patients choose to go with the larger.

Thank you for the question and photographs.  Based on your photographs, I think that you are starting at a great place and should have a very nice outcome with breast augmentation surgery.   
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery (regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work.
2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon. This communication will be critical in determining  breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as  “natural” or "C or D cup”  or "bottom heavy" for example may mean different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate. Again, best not to discuss your goals and/or judge the outcome of the procedure performed based on achieving a specific cup size. The use of pre operative computer imaging may be very helpful. 
 3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery. I generally select appropriate breast implant size/profile after the use of temporary intraoperative sizers and viewing the patient's chest in the upright and supine positions.
I hope this ,and the attached link (dedicated to breast augmentation surgery concerns), helps.