Dr. Pousti is right: communication and having realistic expectations is the key to avoiding disappointment.
The rough estimate is about 175 cc per cup size increase. In some patients more is needed. And it is a rough guide at best.
Therefore if you wanted 2 full cup sizes bigger after your first operation, you would need about 350 cc more in each implant, totalling nearly about twice as large as the first time, about 700 cc. Those are large implants for someone your height and frame size with little breast tissue to begin with.
At some point, when is enough, enough? Big implants lead to thinning of the tissues, more rippling, more droop, and sometimes back pain.
If you were in my office, I would recommend you wait at least 6 months before deciding to go ahead with yet another operation.
I am sorry to hear about your dissatisfaction after breast surgery. What most likely “went wrong” is a failure to communicate goals (between patient and plastic surgeon) carefully enough. As you know, cup sizes will vary from one bra manufactured to another; therefore, discussing your goals ( or judging the outcome of the procedure performed) is based on cup sizes can easily be a source of miscommunication. Although impossible to say in your case, sometimes a patient's anatomy will dictate how large of a breast implant ( and how large of a final outcome) can be utilized. Best, for more accurate/specific information to address your concerns ( in a calm and constructive fashion) with your plastic surgeon. Best wishes.
A change from 360 to 505 should be a nice change. Going too big may not have been appropriate for your body.