Sientra classic 370cc to larger for petite size person?

are determined by patient choice and limited by patient anatomy.  If you have a wide space between your mounds, your implants will have to exceed the natural breast dimensions and I've done this my entire career with only minimal complications.  You should be choosing the volume and your surgeon should be picking the profile to best fit your needs.  And you can ask your surgeon just how close your mounds will be post op and decide if your surgeon picked the right style/profile.

Very difficult to say; you should have had an implant sizing to determine the proper size. Have to make sure that the implant radius won't be longer than the nipple to inframammary fold distance.

From your photo and dimensions, I don't think a 370 cc implant would be too large for your frame.  Ask your surgeon if you could try the implants on in a bra.  This should give you a good idea as to how they will look and how heavy they might feel.  Best wishes, Dr. Lepore. 

At your height and weight and with as much natural breast tissue as you have I think it very likely something under 300cc will get you close to a D look. Of course no one can say for sure without an exam. I think sometimes a surgeon will determine your breast width and then pick the appropriate volume implant without giving any thought to how much tissue you are starting with.