Tissue expanders and reconstruction

Hi Julie, I have recently joined BCNA & came across your discussion thread. A few months have passed now since your last post on this thread & I am hoping all has gone well for you. I had a double mastectomy in August with immediate insertion of tissue expanders. I too have one expander sitting very high which I have been advised will be corrected at time of exchange. I currently have 450ml in each side & am finding it difficult to determine what volume I should be expanded to for the desired final size as it is so difficult to tell with these odd shaped expanders!! Are you aware of any guide as to what the expander volume should be to achieve a particular cup size? Also, did your ps recommend expansion beyond the volume of the final implants & if yes, by how much? Thankyou in anticipation of your reply. Cheers Deb