What size implant for fullness on top but not size increase?

Thank you for the question. Generally speaking, patients undergoing the breast augmentation/lifting combination operation should understand that it is significantly more complex than breast augmentation surgery only and that it is associated with a significantly higher risk of complications and need for additional surgery. 
Also, patients undergoing the combination breast augmentation/lifting surgery should understand that there are limits as to how large of an outcome can be achieved, given that breast lifting surgery does involve breast skin removal. On the one hand, breast augmentation surgery is expanding the breast skin “envelope” while breast lifting is (by definition) tightening up the breast skin envelope. These 2 forces are counteracting each other. 
Therefore, it becomes important to remove the appropriate amount of breast skin and to use the appropriate size/profile of breast implants to balance these 2 forces appropriately and to allow for achievement of the patient's goals while minimizing risks of complications. 
 Generally speaking, the best online advice I can give to ladies who are considering breast augmentation/lifting 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. Again, have a full discussion and communication regarding your desired goals with your plastic surgeon. This communication will be critical in determining which operation and/or 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 “fulness on top” or "C or D cup" etc means different things to different people and therefore prove unhelpful.
Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup size may also be inaccurate. The use of computer imaging may be very helpful during this communication phase.
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. The use of temporary intraoperative sizers with the patient in the upright position makes selection of the best breast implant size/profile relatively easy.
I hope this, and the attached link (dedicated to breast augmentation/lifting surgery concerns), helps.

To just get upper pole fullness there are two good options.  The first is to redo the lift and reposition the lower breast tissue to the upper breast.  I call this an auto augmentation...the lower tissue augments the upper.  It is not always possible depending on what you had done last time.That brings us to option two which is a lift with some fat grafting to the upper breast.  By the very nature of adding fat, the volume will go up some, but it is far less as you are only targeting a specific portion of the breast that is deficient.  As with any fat grafting, it is best to go to a surgeon that does a lot of it.  Otherwise you will pay but may not receive the best fat transfer survival...ie. less volume than you hoped for.Dr. Rodger Shortt is a plastic surgeon in Oakville, Ontario.  His strives to provide the best plastic surgery results and care.  He is one of few plastic surgeons in Canada with a top rating on RealSelf, RateMD and Ontario Doctor Review.  He is the Director of Cosmetic Surgery Training Program and an Assistant Clinical Professor at McMaster University.

Hello and thank you for your question.  The
best advice you can receive is from an in-person consultation.  Based on your description placing a small implant with a lift is a great solution for the problem you have.  This is a common situation for some patients years after breast reduction.   The size,
profile, and shape of the implant is based on your desired breast
size/shape, your chest wall measurements, and soft tissue quality. 
This decision should be based on a detailed discussion with
equal input from both you and your surgeon.   Make sure you
specifically look at before and after pictures of real patients who have
had this surgery performed by your surgeon and evaluate their
results.   The most important aspect is to find a surgeon you are
comfortable with. I recommend that you seek consultation with a qualified
board-certified plastic surgeon who can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon