Debating on 650cc's mod plus or 750cc'ss high profile. 5'1, 113 lbs. Is 750cc HP totally out of proportion with my body?

Whether you decide to go with moderate plus or high-profile depends on your examination. The volume is a bit more subjective. If you have a very narrow chest and desire significant volume in the high-profile implant is a better selection.

Dear Marcy,Please, please re-consider! Large implants in a petite frame like yours are unstable and can cause a number of complications.Pain, ptosis, displacement, etc. Just to name the obvious. Bigger is not always better.Best wishes,Gary Horndeski M.D.

Thank you for the question.  Ultimately, careful communication of your goals (in my practice I prefer the use of goal pictures and direct examination/communication in front of a full-length mirror) will be critical.
Generally speaking, the best online advice I can give to ladies who are considering revisionary 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 “porn star” or  “out of proportion” etc means 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.
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 ( after the use of temporary intraoperative sizers).
I hope this, and the attached link (dedicated to revisionary breast surgery concerns), helps.