Moderate plus or high profile?

Unfortunately the moderate though remarkable pectum excavatum deformity makes impossible a very close cleavage. Nevertheless the highest cleavage occupation is achieved with subfascial plane location of implants, which (among other adavantages) allows exceeding the anatomical barrier posed by the pectoralis tendon insertion on rib cartilages.The optimization is achieved with a good implant base size choice, and not thinking in cc or gr, that is absurd.

A moderate plus implant would be better since you have such little breast tissue.  This shape would result in a more natural breast shape that will fill the gap better than a high profile implant. 

You need to be seen in person to perform an appropriate exam and review your goals.  Choosing an implant without doing so is difficult.

I believe you are on the right path.  I would choose silicone, under the muscle in the 300 cc range.  You should look nice; small C or large B cup when finished.Good Luck!

Thank you for the question. As you know your anatomic starting point will to some degree determine how much space will be present between your breasts after breast augmentation surgery.  Other factors involved include careful breast implant pocket dissection and careful selection of breast implant size/profile.  Remember (when it comes to breast implant pocket dissection and achievement of ideal breast implant cleavage) that each nipple/areola complex must be centered on each breast mound.
Ultimately, careful communication of your goals (in my practice I prefer the use of goal pictures, direct examination/communication in front of a full-length mirror, in bra sizers, and computer imaging) as well as careful measurements (dimensional planning) will be critical.
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. For example, I have found that the use of words such as “natural” or "C cup" 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. Again, the use of computer imaging has been very helpful during the communication process, in our practice.
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 breast augmentation surgery concerns) helps. Best wishes for an outcome that you will be very pleased with. 

With a good surgeon and the correct implants you can narrow the gap but you'll not be able to get rid of it. As to the correct implant size and style, that can only be determined after an examination.