The recto-vesical pouch (http://en.wikipedia.org/wiki/Rectovesical_pouch) is the lowest point of the peritoneum in an anatomical male.
As Anne Lawrence points out in Notes on Genital Dimensions (http://www.annelawrence.com/twr/genitaldimensions.html), without entering the peritoneal cavity the depth of a neo-vagina is limited to approximately 5.5".
On the other hand, Dr. Suporn states that with his technique (http://www.supornclinic.com/restricted/SRS/SRSTechnique.aspx):
QuoteMaximum vaginal depth attained with the scrotal skin graft beyond the original position of the peritoneal reflection (Douglas Pouch).
This seems to indicate that during SRS surgery he positions the peritoneal reflection higher somehow.
Can anyone shed any light on this?